derkesen thesis against scepticism

7/28/2019 Derkesen Thesis Against Scepticism

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HOLY APOSTLES COLLEGE & SEMINARY

AGAINST THE SKEPTICS:

HOW THOMISTIC REALISM REFUTES RADICAL SKEPTICISM

A THESIS PAPER SUBMITTED IN CANDIDACY

FOR THE DEGREE OF MASTER OF ARTS IN PHILOSOPHY

BY

MARIO DERKSEN

CORAL SPRINGS, FLORIDA

JANUARY 8, 2004 A.D.


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Outline

I. Introduction

II. Skepticism and Modernity

1. Origin, Nature, and Scope of Modern Skepticism

2. Skepticism and the Critical Problem

3. Realism and Skepticism

III. The Workings of Human Knowledge According to the Aristotelian-Thomistic

Tradition

4. The Nature of Man as Key to Understanding Knowledge

5. How We Know Things

6. Knowledge and Existence

IV. Response to the Skeptical Challenge

7. Presuppositions and their Justification

8. On Truth

9. The Representative Theory of Perception

10. Of Dreams and Illusions

11. Of Brains and Vats

12. Possibility and Probability

13. Artificial Problem, Artificial Solutions

V. Conclusion: Summary and Evaluation


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I. INTRODUCTION

The Thomist refuses to admit any gap between mind and things.

Frederick Wilhelmsen1

When, in 1879, Pope Leo XIII published his encyclical letter Aeterni Patris on the

restoration of true Christian philosophy, he did so because he realized that unless there

rise up strong Catholic philosophers willing to take on the philosophical challenges put

forth by modern philosophy, countless souls would be deceived by the menacing errors

that had sprung up since the time of the late Renaissance and Ren Descartes, and which

were still threateningperhaps then more than ever beforeto undermine the intellec-

tual and spiritual truths known by reason and divine revelation. Pope Leo recognized that

the evils afflicting and endangering society at his time were due to the false conclusions

concerning divine and human things, which originated in the schools of [false] philoso-

phy and which had already been accepted by the common consent of the masses.2

Thus, the Pope set out to restore true Christian philosophy in the world by calling for a

revival in the philosophy of St. Thomas Aquinas (1225-1274), for the common temporal

good and the salvation of souls.

In keeping with this spirit, and for the refutation of prevailing errors,3 we shall

devote this study to exploring the philosophical wisdom of St. Thomas Aquinas and his

legacy, and to applying it to the fundamental error in modern philosophy that has come to

be known as the critical problem: the question of whether there exists anything outside

1 Frederick D. Wilhelmsen,Mans Knowledge of Reality: An Introduction to Thomistic Epistemology(Englewood Cliffs, NJ: Prentice-Hall, 1956), p. 40.2 Pope Leo XIII, Encyclical LetterAeterni Patris, August 4, 1879 (Boston, MA: Pauline Books & Media,n.d.), par. 2, p. 4.3 Ibid., par. 31, p. 21.


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of the knowing subject and, if so, whether there can be true knowledge of these things.

Essentially originating with Ren Descartes (1596-1650), this critical problem has

become so influential that any epistemologist, Thomistic or not, writing in the post-

Cartesian era is now expected to analyze it, to comment on it, and perhaps even to use it

as the starting point of his epistemological investigation.

It was about this critical problem, which puts into question the existence of a world

outside the mind, that the existentialist Martin Heidegger remarked: The scandal of

philosophy is not that this proof [that there is a connection between the in me and the

outside of me] has yet to be given, but that such proofs are expected and attempted

again and again.4 Though Heidegger, of course, would disagree with the solution

proposed in this paper (inasmuch as for him, man in his very being is already totally

involved with the world he seeks to understand, and so Heidegger would take the

objective knowing of Thomistic realism as a deformation of that more basic

immersion in the world) and would challenge the Thomistic realist on a different level,

we remain undaunted in our endeavor to answer modern skepticism cogently and

compellingly by means of the golden wisdom of St. Thomas5 and the Aristotelian-

Thomistic realist tradition.

We thus propose to argue in this paper that a sound investigation into the study of

knowledge reveals that the so-called critical problem is merely contrived, based on

false premises, and does not present a genuine challenge to the justification of objective

knowledge, inasmuch as the problem can be reduced to absurdity and is based on gratui-

tous assumptions about the nature of knowledge and the knowing subject. We will com-

4 Martin Heidegger, Being and Time, trans. John Macquarrie and Edward Robinson (New York, NY:Harper & Row, 1962), p. 249; italics given.5 Leo XIII, Aeterni Patris, par. 31, p. 21.


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bat the critical problem by assuming at the outsetand later validatethe pre-critical

attitude by explaining through the use of it why the critical paradigm is not warranted.

Since the pre-critical paradigm, i.e., the realist Aristotelian-Thomistic paradigm, does not

run into the same problems as the Cartesian critical paradigm does, and since it avoids the

critical problem and can answer skeptical objections raised against it, we will conclude

that the critical problem is an artificially-created pseudo-problem and must therefore be

rejected.


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II. SKEPTICISM AND MODERNITY

1. ORIGIN, NATURE, AND SCOPE OF MODERN SKEPTICISM

Men are most anxious to find truth, but very reluctant to accept it.

Etienne Gilson6

Though it enjoyed a major revival after the Renaissance, epistemological skepticism

was by no means new in the seventeenth century. It is difficult to pinpoint exactly who

the first skeptic was, as skeptical thinkers can be found in Pre-Socratic times, but we

can say that the first philosopher who took a serious skeptical stance in a systematized

fashion was Pyrrho of Elis.7 His skeptical position came to be referred to as

Pyrrhonism and was taken up and defended centuries later by Sextus Empiricus (ca.

200 A.D.). Though Pyrrhonism had all but disappeared during the middle ages, it made

its comeback in the thought of Michel de Montaigne (1533-1592), Pirre Charron, and

Francis Snchez, after SextussOutlines of Pyrrhonismhad been translated into Latin and

thus been made available to the scholars of the Renaissance.

Skepticismsimpliciter is difficult to define, as the precise meaning of the notion is

contested by different thinkers who all claim to be skeptics.8 Etymologically speaking, a

skeptic is someone who examines, deriving from the Greek word skeptesthai, to

examine. In the ancient tradition, the Pyrrhonists held to a differentand more sophisti-

cated, I venture to saykind of skepticism than the Academics. For Pyrrho, skepticism

consists in the suspension of judgment, i.e., the refusal to affirm or deny one claim over

6 Etienne Gilson,The Unity of Philosophical Experience(San Francisco, CA: Ignatius Press, 1999), p. 49.7 See R. J. Hankinson,The Sceptics (New York, NY : Routledge, 1995), p. 31.8 See ibid., pp. 13-18.


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another, because to every account an equal account is opposed.9 Thus it is that the

Pyrrhonian skeptic holds no beliefs. The intended end for which he engages in the sus-

pension of judgment is tranquility (ataraxia), the freedom from disturbance about what

may or may not in fact be the case. Hence, Pyrrhonism actually intended to be a practical

philosophy, a way of life.

The skeptics of the later Platonic Academy, on the other hand, viewed skepticism dif-

ferently. Their skepticism was simply a denial of knowledge: nothing can be known,

nothing can be affirmed with certainty. That is, the major distinction between the Aca-

demic and the Pyrrhonist is that the Academic positively claims that nothing can be

known, whereas the Pyrrhonist merely says that as far as he can see, there is not enough

evidence for assenting to one position rather than its opposite, though such evidence may

very well appear in the future.10 Sextus saw the Academic stance so far removed from

that of Pyrrhonism that he denied the Academics the label of skeptics and simply

referred to them as Academics. In fact, we may classify the Academics as negative

dogmatists, inasmuch as they deny (hence negative) the possibility of knowledge,

which, however, is in itself a positiveknowledge claim(hence dogmatic).11 It is readily

obvious that this position carries with it an inconsistency that leads to its own refutation.

When battling the Academics, St. Augustine was not hesitant to point out that if their

9 Sextus Empiricus, Outlines of Scepticism, ed. Julia Annas and Jonathan Barnes (New York, NY:Cambridge University Press, 2000), I:12, p. 6. In I:202, Sextus explains that he is speaking of accounts thatallege to establish the truth about something unclear. That is, the Pyrrhonist does not question absolutelyeverything, e.g., his appearances or the fact that he is suspending judgment.10 See ibid., I:226, p. 59.11 Cf. Hankinson,The Sceptics, pp. 14-16.


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denial of the possibility of knowledge is true, then a man who knows merely it [the

denial] itself, knows some truth.12

During the time of the Renaissance, SextussOutlineswere translated into Latin, and

thus Pyrrhonism was carried into the dawn of modernity, though the road to skepticism

had already been paved by what Etienne Gilson (1884-1978) labels the psychologism

of William of Ockham.13 Among the Renaissance skeptics was Michel de Montaigne,

whose thought, as it turned out, provided the bridge over which philosophy would

travelby means of the influence it had on Ren Descartesfrom post-medieval phi-

losophy into modernity.

In his Essays, Montaigne essentially revived the arguments of the Pyrrhonists, not

those of the Academics. He concluded that only divine illumination and revelation, not

philosophy or reason, give true certainty:

Since the senses cannot decide our dispute, being themselves full of uncertainty, it mustbe reason that does so. No reason can be established without another reason: there we goretreating back to infinity.14

[Man] will rise, if God by exception lends him a hand; he will rise by abandoning andrenouncing his own means, and letting himself be raised and uplifted by purely celestialmeans.15

It is perhaps not surprising that Montaigne should have taken this position, or that skepti-

cism in general should have resurfaced during the Renaissance, given the numerous quar-

rels over philosophical and theological matters of the thinkers of the high and late middle

ages. As Gilson relates:

There is never too much of a good thing, but there were too many varieties of the samething, and the difficulty was that since Ockham was refuting Duns Scotus, the while Duns

12 St. Augustine,Against the Academics [Contra Academicos], trans. John J. OMeara (New York, NY:Paulist Press, 1978), III:18, p. 118.13 See Gilson, Philosophical Experience, pp. 69-72.14 Michel de Montaigne, Apology for Raymond Sebond, ll. 692-95, inSelections fromthe Essays, trans.Donald M. Frame (Arlington Heights, IL: AHM Publishing, 1972), p. 68.15 Ibid., ll. 811-14, p. 71.


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Scotus was correcting Bonaventura, or Thomas Aquinas straightening out AlbertusMagnus, they could not all be right at the same time. But who was right?

By far the easiest way to solve the problem was to decide that every one waswrong.16

In his Discourse on the Method, Descartes struggled to free himself from the skepticism

that Montaigne had revived, triggered by the endless disputations of the scholastics:

I will say nothing about philosophy but that, seeing that it has been cultivated for manyages by the most excellent minds that have lived, . . . nonetheless, there is still not to befound in it anything about which one does not dispute, and which, as a consequence, notbe doubtful. . . .17

Greatly troubled by these uncertainties and by the corresponding doubt gushing forth

from them, Descartes took the radical and revolutionary step to consider as well nigh

false all that which was merely probable.18 The moment he had made this seemingly

innocuous decision, he had given birth, as it were, to modern philosophy.

Doubting a claim is one thingdeclaring it well nigh false on the mere grounds

that it is uncertain is quite another. In the face of uncertainty, the correct attitude that rea-

son demands one adopt is that of epoch, as the ancient Greeks would say, i.e., that of

suspension of judgment. If I do not know whether I should assent to or oppose some-

thing, the reasonable course of action is to do neither, to simply refuse judgment until the

issue at hand becomes clearer.

The real crux of the matter, however, is different and more far-reaching still. Regard-

less of whether Descartes should have suspended judgment about, rather than considering

false, that which was merely probable,19 his procedure of discerning the true from the

16 Gilson, Philosophical Experience, p. 74.17 Ren Descartes,Discours de la mthode/Discourse on the Method: A Bilingual Edition with anInterpretive Essay, trans. George Heffernan (Notre Dame, IN: University of Notre Dame Press, 1994), I:12,p. 21.18 Ibid.19 In fact, in hisMeditations on First Philosophy, Descartes does say he merely withholds assent, but hedoes so just as carefully as I do from those [opinions] which are patently false. See Ren Descartes,


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falsehis litmus test, in other wordsis what really constituted the break with all past

philosophy. The first step he was convinced he needed to take was the radical expulsion

of all opinions and views he had ever held, even those he thought he knew:

I was persuaded that . . . for all the opinions to which I had hitherto given credence, Icould not do better than to undertake, once and for all, to get rid of them, in order toreplace them afterwards either by other, better ones, or even by the same ones, when Iwould have adjusted them to the level of reason. And I firmly believed that I would, bythis means, succeed in conducting my life much better than if I were to build only on oldfoundations and to rely only on the principles of which I had let myself be persuaded inmy youth, without ever having examined whether they were true.20

In other words, he wanted a clean slate, starting all over again from the bottom up. All

prior knowledge, belief, and opinion should be eradicated. This was the necessary pre-

condition for his plan to rebuild the house of knowledge on a completely certain

foundation, as he makes clear in hisMeditations on First Philosophy:

For the purpose of rejecting all my opinions, it will be enough if I find in each of them atleast some reason for doubt. And to do this I will not need to run through them allindividually. . . . Once the foundations of a building are undermined, anything built onthem collapses of its own accord; so I will go straight for the basic principles on which allmy former beliefs rested.21

Thus was triggered the avalanche of radical skepticism in modern philosophy.

Descartes is, of course, the modern skeptic par excellence.22 Never before in the his-

tory of Western philosophy had anyone doubted so radically and systematically as he.

Though the ancient skeptics and also the Renaissance Pyrrhonists all doubted as a matter

of principle, none of them had actually called into question the existence of a world out-

side the mind: Greek philosophy does not know the problem of proving in a general way

the existence of an external world. That problem is a modern invention. . . .23 For

Meditations on First Philosophy, trans. John Cottingham (New York, NY: Cambridge University Press,1996), I, p. 12.20 Descartes, Discourse on the Method, II:2, p. 29.21 Descartes, Meditations, I, p. 12.22 This statement needs qualification, which will be given below.23 M. F. Burnyeat, Idealism and Greek Philosophy: What Descartes Saw and Berkeley Missed,Philosophical Review90 (1982): p. 19.


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Descartes, doubting the existence of the external world was simply necessary in order to

be consistent in his method of doubting everything it was possible to doubt:

I will suppose . . . that not God, who is supremely good and the source of truth, but rathersome malicious demon of the utmost power and cunning has employed all his energies inorder to deceive me. I shall think that the sky, the air, the earth, colours, shapes, soundsand all external things are merely the delusions of dreams which he has devised toensnare my judgment. I shall consider myself as not having hands or eyes, or flesh, orblood or senses, but as falsely believing that I have all these things.24

As radical as this doubt is, Descartes was fully aware that he was merely pretending for

a time25 and not really calling this into question. His doubt was merely methodical,

engaged in so that he could arrive at some point which is impossible to doubtif such a

point was to be found.

This, then, is another point on which Descartes differs from the ancient skeptics. The

Pyrrhonists doubt was practical, aimed at a tranquil life, and therefore real; Descartes

doubt was a matter of method to find an indubitable principle, and it was therefore not to

be taken as genuine. This fact explains why the scope of Descartes skepticism was

greater than that of the Pyrrhonists; it encompassedor so he thought26absolutely

everything that was dubitable. Paradoxically, however, Descartes only doubted exces-

sively in order ultimately to defeatskepticism27beating the skeptic at his own game, so

to speak. Once he had found his indubitable basis from which to start rebuilding the

house of knowledge, he would make sure that all knowledge claims would be immune

from skeptical attack. He would finally be able to have certitude regarding his knowl-

edge. Thus it was necessary for him to make his doubt global.

24 Descartes, Meditations, I, p. 15.25 Ibid.26 For instance, Descartes never made an effort to doubt the rules of logic or to doubt his very ownmethodical doubt as a proper method for arriving at certainty.27 Cf. Descartes, Discourse on the Method, III:6, p. 47.


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2. SKEPTICISM AND THE CRITICAL PROBLEM

It would be impossible to investigate, enumerate, and analyze all of the errors and in-

consistencies in Descartes epistemology and method here. Such is not the intention of

this paper. However, we must pay close attention to the fundamental change in the subse-

quent philosophy it engendered, and to the radical skepticism it, even if unwittingly, pre-

cipitated.

Closely bound up with Descartes radical doubt is what has come to be known as the

critique of knowledge or simply the critical problem. The indubitable ground to

which Descartes finally came, his Archimedean point, as it were, was, of course, the

Cogito: Cogito, ergo sum I think, therefore, I am.28 But this basis led him to identify

the ego, the I, merely with thought, not with the composite of body and soul as had

been the traditional Aristotelian and Christian view of the self: Thought; this alone is

inseparable from me. . . . I am, then, in the strict sense only a thing that thinks; that is, I

am a mind, . . . or intellect. . . .29 He was even more explicit about this conclusion in the

Sixth Meditation: I am really distinct from my body, and can exist without it.30

The result of this radical bifurcation between the mind and the body, perhaps some-

what reminiscent of Plato, but still essentially unprecedented in Western philosophy up

until this point, led to an exaggerated view of the mind and gave way to epistemology as

a starting point from which all subsequent philosophical inquiry needed to proceed. From

then on, all philosophy was supposed to start with the subject, with the I, and the exis-

tence of everything that is not I, would first need to be proved. This is precisely what

makes up the so-called critical problem:

28 See Descartes, Discourse on the Method, IV:1, p. 51.29 Descartes, Meditations, II, p. 18.30 Ibid., VI, p. 54.


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If I am philosophicallythat is, criticallycertain of only one thing at the outset of myphilosophizing, and if this one thing is the existence of myself as a thinking principle,then how am I able (if I am able at all) to move from this primitive certitude to aknowledge of other things, and, most especially, to a knowledge of the existence of theextra-mental world, of things existing independently of my own understanding.31

Since I have arrived at theCogito only through excessive doubt, how can I move from

the thinking self to the world without abandoning the skeptical method which I put into

place in order to keep myself from deception and false knowledge claims?

Though Descartes provided an answer to this question, most every thinker agrees that

his answer was insufficient. The Frenchman relied on a few dubious a priori arguments32

for the existence of God and tried to infer from them that God, being all-good, would

never let anyone be deceived about anything he perceives clearly and distinctly.33 One

may express surprise at such a facile solution in the face of the otherwise rigorous

Cartesian process of ensuring that every possibility of error is avoided. Descartes over-

confidence in this answer can perhaps be explained by the fact that there was really no

other way in which he could have solved the conundrum into which he had put himself.

With theCogito, Descartes had accomplished the turn to the subject in philosophy

his very own Copernican Revolution, one without which Kants would have never seen

the light of day. Prior to Descartes, philosophical inquiry had begun with things, with the

world, and hence with natural philosophy. From then on, however, all philosophizing was

to begin with thought and with doubt. The critical problem he had createdyes, created,

not discovered, as will be shown laterwould ensure that subsequent philosophers would

always recognize the primacy of the thinking self, the subject, and try to work their way

31 Wilhelmsen, Mans Knowledge of Reality, p. 14.32 Among others, Descartes used a modified version of St. Anselms ontological argument. SeeMeditations, III, pp. 24-36, andDiscourse on the Method, IV:5, pp. 55-57.33 Descartes, Meditations, III, p. 24. See also Descartes replies to the seventh set of objections, where henonchalantly claims that nothing can be clearly and distinctly perceived . . . without being true (ibid., p.67).


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out into the world, the object: It was Descartes who put subjective knowledge at the

center of epistemologyand thereby made idealism a possible position for a modern

philosopher to take.34 It is not surprising, therefore, that the thinkers following Descartes

all accepted his revolution and started with the subject, though with the most striking dif-

ferences: Malebranche, Spinoza, Leibniz, Locke, Berkeley, Hume, Kant, and Hegel, to

name just a few. In one way or another, all of them were idealists.

The critical problem is really the ultimate fruit of hyperbolic doubt, which is its only

motivation. By unmasking it as a pseudo-problem, however, we can counter the skeptical

attack in a way which is detrimental to all future attempts at irrational doubt. When we

look closely at the origins of the critical problem in Descartes, we find that, far from

doubting absolutely everything that is dubitable, Descartes actually presupposes as true

the representative theory of perception. According to this position, the mind is a pas-

sive container which receives little sense-images, or ideas, of the things in the outside

world. What the mind is directly aware of is not the thing outside the mind, but only the

representation of the thing inside the mind. This sense image is the mediator between

the mind and the world. Thus the difficulty arises as to how we can know that the repre-

sentations inside the mind are true representations of the things in the world and do not

give us a false picture of extra-mental reality. Of course, this difficulty can never be re-

solved, as all the access we have to the world outside the mind is through sense percep-

tion, and if we take this view of how perception works, then it is impossible to validate

our beliefs and knowledge claims about extra-mental reality.35

34 Burnyeat, Idealism and Greek Philosophy, p. 33.35 We will critically examine this theory in more detail in chapter 8.


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Without this theory of perception or one like it, however, the excessive Cartesian

doubt is not possible, and the radical turn to the subject is therefore also thwarted. As a

result we can say that the persuasiveness of the critique of knowledge and, thus, also the

persuasiveness of extreme skepticism depend to a large extent on the tenability of the

representative theory of perception, a position which Descartes ironically took for

granted. Since, however, the representative theory of perception was endorsed by virtu-

ally every modern philosopher,36 it is clear why the critical problem was the fundamental

difficulty and starting point from which these thinkers proceeded. A few comments on

perception, knowledge, and skepticism are therefore in order now.

3. REALISM AND SKEPTICISM

As I already suggested, the critical problem as stated, i.e., in terms of the representa-

tive theory of perception, cannot be solved. It cannot be solved because the very theory

requires that direct access to the extra-mental world is not possible; but it is precisely this

access which is needed to solve the critical problem. In other words, the theory necessi-

tates that the only evidence which could refute it is inadmissible. Thus it has made itself

non-falsifiable in principle. This is why Gilson can state that it is an illusion to think that

one can extract an ontology from an epistemology, and, by this or that method, discover

in thought anything apart from thought.37 Since the critical problem begins with the

mind and takes, as it must, the representative theory of perception as true, it necessarily

follows that whatsoever we entertain in order to refute this theory, it will necessarily be in

36 The one thinker most clearly endorsing it was perhaps John Locke (1632-1704). See John Locke,AnEssay Concerning Human Understanding(Amherst, NY: Prometheus Books, 1995), IV:I.1, p. 424.37 Etienne Gilson, Methodical Realism, trans. Philip Trower (Front Royal, VA: Christendom Press, 1990),p. 29.


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the order of thought, i.e., inside the mind; and so the critique of knowledge precludes its

own solution by its premises. After all, we can never step outside of ourselves and

compare the representational image with the object of which it is the image, since all of

our access to this object is by means of the image, according to the theory.

Not surprisingly, therefore, many representationalists38 claim that we can have no

knowledge of the outside world. But here we must ask ourselves whether what they mean

by knowledge is still the same as what the realist understands by the term. For the

realist, there is no such radical bifurcation between the inside (i.e., mental) and

outside (i.e., extra-mental) world, seeing that the subject and recipient of knowledge is

always aman,39 composed of body and soul, i.e., matter and form, and exists therefore as

partly mental and partly extra-mental.40 Man, then, in his very being, has already bridged

the gap that the radical skeptic has created for himself. One may surely ask, therefore,

why the realist should be troubled by the representationalists claim to the impossibility

of knowledgeknowledge which, on the representationalists own admission, is not the

knowledge of things anyway but only the knowledge of ideas. The notion of knowledge

as the common man understands it is, by definition, realistic. That is to say, the only way

we can be truly said to knowthat there is a rose is if we actually have direct access to the

rose itself, not access to a mere representation of the rose.

It is expedient, therefore, to investigate the nature of empirical knowledge. We must

closely investigate what empirical knowledge is and how it is acquired. To do so, we

shall explore, quite uncritically for the moment, the epistemology of the Aristotelian-

38 For purposes of this paper, I am treating representationalist, idealist, and (radical) skepticsynonymously, unless otherwise indicated.39 See St. Thomas Aquinas,Truth, vol. 1, trans. Robert W. Mulligan (Indianapolis, IN: Hackett PublishingCo., 1994), q. 2, art. 6, ad. 3, p. 94. Cf. Aristotle,De Anima, 408b15.40 Cf. Celestine Bittle, Reality and the Mind (Milwaukee, WI: Bruce Publishing Co., 1936), pp. 83f.


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Thomistic tradition to see what insights it can give us into the nature of knowledge and

the workings of the human mind. We shall later see how we can validate this tradition in

the face of skeptical attacks and the representative theory of knowledge.


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III. THE WORKINGS OF HUMAN KNOWLEDGE ACCORDING TO THE

ARISTOTELIAN TRADITION

It is the real things immediately and directly presented by sensationthat are the soil in which our intellectual life takes root and grows.

John F. X. Knasas41

Aristotle (384-322 B.C.) opens his Metaphysics with the observation that [a]ll men

naturally desire to know.42 Such a desire can only be explained if knowledge is indeed

possible, for the acquisition of knowledge is the final cause for which the desire exists.

No one in the scholastic realist tradition ever doubted the possibility of knowledge. That

knowledge is possible was self-evident to the scholastics, proven quite simply by the fact

that knowing is something we do all the time. Someone who swims does not wonder

about whether swimming is possible; he knows it is possible because he does it. It is,

however, quite legitimate to inquirehowknowledgeor swimmingis possible, and this

is what we must now investigate.

What, however, is knowledge? Knowledge as such eludes precise definition.43 In the

De Veritate, St. Thomas Aquinas points out that three things are necessary for there to be

knowledge: an active power in the knower by which he judges about things, a thing

known, and the union of both.44 Knowledge is a quality of the soul that is had when the

knower becomes the thing known in an intentional way. To understand what this means

41 John F. X. Knasas,Being and Some Twentieth-Century Thomists (New York, NY: Fordham UniversityPress, 2003), p. 34.42 Aristotle, Metaphysics, 980a21. Translation taken from St. Thomas Aquinas,Commentary on AristotlesMetaphysics, trans. John P. Rowan, rev. ed. (Notre Dame, IN: Dumb Ox Books, 1995).43 See, e.g., Bittle,Reality and the Mind, pp. 14f.; George P. K lubertanz,The Philosophy of Human Nature(New York, NY : Appleton-Century-Crofts, 1953), pp. 82f.44 Aquinas,Truth, vol. 1, p. 54, q. 2, art. 1, ad cont. 3.


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and why this is important, we must first consider the nature of man, since the knowing

subject in our discussion is always a human being.

4. THE NATURE OF MAN AS KEY TO UNDERSTANDING KNOWLEDGE

The radical skeptics presuppose, without questioning it, a Platonic conception of man.

This goes to show that it is really impossible to philosophize about knowing without first

having a clear picture of the nature of man (and thus presupposing that at least some

knowledge is possible). This is so because knowledge is never found in a vacuum but

always as a relation between a knowing subject and a known object; it is necessarily

relational. It is crucial, therefore, not to fall into error with regards to both who the

knower is and what kinds of things are knowable.

According to Plato, man is a soul trapped in a body,45 and there is no essential

connection between the two; in fact, the two are, as it were, at war with one another. The

soul is the real self, and the body is only a prison from which the soul longs to free itself.

Reality is mental in nature and grasped abstractly; everything physical is not really real,

only part of a shadow world, and sensation cannot give us true knowledge. With this

view in mind, the idealist struggles to explain the experience of knowledge and concludes

either that knowledge is not possible but mere illusion (e.g., Hume, Unger), or he invents

more or less bizarre arguments which must be accepted in order to have knowledge after

all (e.g., Descartes, Leibniz, Kant).

The Platonic view of man is false, however, as Aristotle showed. Man is not two

independent things, a soul and a body, but one unified whole, a body whose form, i.e.,

45 See Plato, Phaedrus, 250, in John M. Cooper, ed., Plato: Complete Works(Indianapolis, IN: HackettPublishing Co., 1997), p. 527.


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formal cause, is the soul: The soul is the cause or source of the living body.46

St. Thomas repeats Aristotles teaching when he says that the intellect which is the prin-

ciple of intellectual operation is the form of the human body.47 This view is based, of

course, on Aristotles general teaching of hylomorphism, according to which all physi-

cal entities are composed of matter (Greek, hyle) and form (Greek, morphe): [N]ature

has two senses, the form and the matter. . . .48 We cannot go here into all the reasons

why Aristotles account of human nature is superior to Platos, but one can see that it is

so even onprima faciegrounds, as Aristotles position can explain the fact that everyone

experiences himself as a whole and not simply as a soul or mind trapped in a body.

49

As

indicated above, it is necessary to have a sound grasp of human nature, that is, of the

nature of the knowing subject, before one can examine whether and how knowledge is

possible. But this means that the investigation into human nature and human knowing are

necessarily pre-critical, but it does not in fact beg the question of the critical problem,

though it does perhaps show that the problem runs into serious complications at the very

outset. Furthermore, if the critical problem should prove to be a genuine problem after

all, in the post-critical stage, any conclusions about the nature of human knowing and

the processes of knowledge obtained in the pre-critical analysis can still be revised after-

wards. Thus, there is no reason to reject a pre-critical investigation into human nature and

human cognition.

46

Aristotle, De Anima, 415b8. Translation taken from St. Thomas Aquinas,Commentary on AristotlesDe Anima, trans. Kenelm Foster and Silvester Humphries, rev. ed. (Notre Dame, IN: Dumb Ox Books,1994).47 St. Thomas Aquinas,Summa Theologica, vol. 1, trans. Fathers of the English Dominican Province(Allen, TX: Christian Classics, 1981), p. 370, I, q. 76, art. 1.48 Aristotle, Physics, 194a12. Translation taken from St. Thomas Aquinas,Commentary on AristotlesPhysics, trans. Richard J. Blackwell, Richard J. Spath, and W. Edmund Thirlkel, rev. ed. (Notre Dame,IN: Dumb Ox Books, 1995), p. 87.49 Even the skeptic will have to admit that if he is only a mind, then it cannot behewho speaks, types, andwrites about skepticism, since these are all acts of his body.


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5. HOW WE KNOW THINGS

For our purposes, we will only consider empirical knowledge, that is, knowledge of

sensible objects, since this is the kind of knowledge most fundamentally under attack by

the radical skeptics. Later on, in our direct response to the skeptical arguments, we must

also briefly discuss a priori knowledge, i.e., first epistemological principles and the like.

But first, we must turn to the question of the workings of empirical knowledge, even if

the scope of this paper forces us to be brief.

Empirical knowledge is necessarily obtained through perception, which, in turn, is

based upon sensation. Unfortunately, nowadays the notion of sensation is often reduced

to that of mere sight, as though the other four sensestouch, hearing, smell, and taste

were somehow less significant, when in fact, at least in the case of touch, quite the oppo-

site is the case.50 St. Thomas, like Aristotle, was adamant that there is nothing in the intel-

lect that was not first in the senses;51 that is, anything that is received into the mind has

arrived there through sense-perception. This is a far cry, however, from saying that

everything in the mind is limited to sense-experience, as modern empiricists like Hume

would contend. Perception makes empirical knowledge possible because the very notion

of perception implies that there is epistemic access to the extra-mental world, as

Mortimer Adler (1902-2001) points out:

The statement I perceive X is inseparable from the assertion X exists. If X did notexist, it would be imperceptible, and the statement I perceive X would be false. In itsplace, there should be a true statement about menamely, he is hallucinating X.52

50 As Fr. Robert Henle argues, the sense of touch is in fact thebasisfor all epistemological and thusperceptual realism. See Robert J. Henle, The Basis of Philosophical Realism Re-examined,The NewScholasticism56 (1982): pp. 1-29.51 See Aquinas,Summa Theologica, vol. 1, p. 58, I, q. 12, art. 12; St. Thomas Aquinas,Truth, vol. 2, p.121, q. 12, art. 3, ad 2.52 Mortimer J. Adler, Intellect: Mind Over Matter (New York, NY : Macmillan Publishing Co., 1990), p. 96.


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To examine how empirical knowledge works, then, it is expedient to examine the process

of knowledge that moves from sensation via perception to intellection.

Sensation, Aristotle says, is the receiving of forms without matter, which he likens

to the way in which wax receives a seal without the iron or gold of the signet-ring. It

receives an imprint of the gold or bronze, but not as gold or bronze.53 The sensed object

acts upon the sense organ and thus causes an alteration in it, as the signet-ring alters the

wax, thus causing a sense impression. In the example of my touching of a table, the table

receives some sort of existence in me, but not material existence, since the table still

exists outside me as before. Aristotles analogy illustrates what kind of existence it is

instead, namely, a formal existence. The form of the sense-object is received byand

thus becomes present inthe knower, but the form having, in the sense, a different

mode of being from that which it has in the object sensed, as Aquinas explains. In the

object, the form is present in a material mode of being (esse naturale), whereas in the

sense, the form is present in a cognitional and spiritual mode.54 Since the sensed object

does not undergo any change through my sensing it (except perhaps for the sense of

touch, which can modify more delicate objects), we cannot say that sensation receives the

matter of the object; instead, it can only be the form. This is the essential basis for the

process of knowledge.

Sensation is the basis of perception. Perception differs from sensation inasmuch as

perception is a process involving the internal senses and is dependent on the sensation of

the outer senses.55 In fact, it is the internal senses, taken together, that bring the sensing

53 Aristotle, De Anima, 424a18-21.54 Aquinas,Commentary on Aristotles De Anima, p. 172, II, lectio24, no. 553.55 See William A. Wallace,The Modeling of Nature: Philosophy of Science and Philosophy of Nature inSynthesis(Washington, DC: Catholic University of America Press, 1996), p. 134.


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process to completion.56 The four internal sensesthe common sense, imagination,

memory, and the cogitative sense57are responsible for unifying the different sensa-

tions into one coherent whole that lets us truly perceive an object. Whereas sensation

gives us green, spherical, and sweet, it is the internal senses which put these qualities

together and present them as belonging to one and the same object, which is later,

through intellection, identified as an apple. We can say, then, that perception is more

elaborate and advanced than mere sensation and perfects it.

The likenesses received in sensation are called impressed species or sensible

species, whereas those attained in perception are called phantasms.

58

Neither sensible

species nor phantasms must be confused with the Cartesian and post-Cartesian ideas,

which are complete representationsof actual objects. Rather, sensible species and phan-

tasms are likenesses similar to the way in which a mirror-image is a likeness. A man who

looks in the mirror seeshimself, not a representation of himself, but he does so by means

ofthe mirror. So it is with the sensible species and the phantasms and also the intelligible

species, as we will see later. They are not objects of knowledge or perception or sensa-

tion, but themeanswhich make knowledge, perception, and sensation possible.59

The phantasm is an essential component to empirical knowledge, for it links, as it

were, perception and intellection. It does not represent the concrete object, as the

moderns would have it; it simply presents it. As such, the phantasm is necessary, but not

sufficient, for intellectual knowledge; it is a vehicle that makes intellectual knowledge

possible; and so the phantasm is to the intellect as the sense object is to the sense faculty.

56 D. Q. McInerny, Philosophical Psychology(Elmhurst, PA: Alcuin Press, 1999), p. 117.57 Ibid., p. 116.58 See Wilhelmsen,Mans Knowledge of Reality, pp. 95f.59 Cf. Aquinas, Summa Theologica, vol. 1, pp. 433f., I, q. 85, art. 2.


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Hence Aristotle and St. Thomas teach that the soul cannot understand without phan-

tasms.60

Now, in the Aristotelian tradition, the intellect is a particular power, or part, of the

soul: By the powers of the soul, we mean the vegetative, the sensitive, the appetitive, the

locomotive, and the intellectual.61 This intellectual power is both active and passive; that

is, we must distinguish between an active and a passive component in the intellect in or-

der to explain the process of knowledge. By passive intellect is meant the intellects

receptive power, which can be demonstrated to exist by the simple fact that we all experi-

ence not knowing something at one point and knowing it later, e.g., the rules for playing

tennis. The knower is said to pass from the potential state of knowing the rules for play-

ing tennis to the actual state of knowing thembefore, hecouldknow them; then hedoes

know them. This is what St. Thomas and Aristotle mean when they say that with us

[humans] to understand is to be passive.62 Since the mind has the capacity to understand

all earthly things, even though at no point does it ever actually understand them all, we

can say that the passive intellect isall things potentially. . . .63

In addition to the passive component of the intellect, we must also posit an active

component, however. St. Thomas Aquinas explains why this is:

Since then the intellectual part of the soul alternates between potency and act, it mustinclude these two distinct principles: first, a potentiality within which all intelligibleconcepts can be actualized . . . and then, also, a principle whose function it is to actualizethose concepts.64

60 Aquinas,Commentary on Aristotles De Anima, p. 230, III, lectio12, no. 772. Cf. Aristotle, DeAnima, 431a17.61 Aristotle, De Anima, 414a31-32.62 Aquinas,Summa Theologica, vol. 1, p. 397, I, q. 79, art. 2. Cf. Aristotle,De Anima, 429a13-24.63 Aquinas,Summa Theologica, vol. 1, p. 449, I, q. 88, art. 1; italics given.64 Aquinas,Commentary on Aristotles De Anima, p. 219, III, lectio10, no. 728.


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Without the active component, the human intellect would be reduced to a mere receptacle

of sensations, as in the case of brute animals. We could knowparticular trees, stones, and

cabbages, but we could know them only as particular; we could not know what it is to be

a tree, a stone, or a cabbage, and thus that these objects actually are trees, stones, and

cabbages. More abstractly, it would be the purpose of such an active component of the

intellect to render intelligible to the mind the concrete singular object. The mind itself

cannot grasp the object in its singularity because the mind is geared towards universals

only, whereas the sense is exclusively geared towards singulars (and for which reason

brutes, which do not have intellection, cannot know anything but can merely sense

things). But each perceived object is particular, that is, singular and concrete. It is also

necessarily material. The intellect being an immaterial power, however, it cannot receive

that which is material.

How, then, can the immaterial receive that which is material? Properly speaking, it

cannot. St. Thomas teaches that according to the mode of immateriality is the mode of

knowledge.65 That is, the intellect must somehow consider the immaterial aspects of the

sensed object in order to know it, and this it can do only by means of an active compo-

nent, as nothing can act that is not itself in act.66 The phantasm cannot reduce the passive

intellect to act because it is not in act but only in potency with respect to the intelligible

order, since it is enveloped in materialand therefore, properly speaking, non-intelli-

gible67conditions. Hence the passive intellect cannot be actualized by the phantasm,

65 Aquinas,Summa Theologica, vol. 1, p. 72, I, q. 14, art. 1.66 See ibid., p. 452, I, q. 89, art. 1.67 Cf. ibid., p. 72, I, q. 14, art. 1; p. 431, q. 85, art. 1.


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since the intellect can only receive what is actually intelligible, much as the nose can only

smell what actuallyand not just potentiallyhas odor.68

The mind thus needs what the Aristotelian tradition calls the active intellect, a fac-

ulty of the mind that illuminates the phantasm and abstracts from it the intelligible spe-

cies and thus feeding the passive intellect with immaterial and therefore actually intelligi-

ble information: [T]hrough the light of the agent [=active] intellect the forms abstracted

from sensible things are made actually intelligible so that they may be received in the

possible [=passive] intellect.69 Phantasm and active intellect thus work together to pro-

vide the mind, i.e., the passive intellect, with the necessary intelligible species it needs in

order to know the object, as St. Thomas points out: [T]he possible intellect receives

forms whose actual intelligibility is due to the power of the agent intellect, but whose

determinate likeness to things is due to cognition of the phantasms.70 The intelligible

species is thus impressed, as it were, on the passive intellect.

However, since our intellect considers only what it has abstracted (and therefore what

is universal) in the intelligible species, it cannot know the singular directly but must do so

in a roundabout way. This it does by turning again to the phantasm, which presents the

singular in its singularity:

Our intellect cannot know the singular in material things directly and primarily. Thereason of this is that the principle of singularity in material things is individual matter,whereas our intellect, as we have said above (Q. 85, A. 1), understands by abstracting theintelligible species from such matter. Now what is abstracted from individual matter isthe universal. Hence our intellect knows directly the universal only. But indirectly, and asit were by a kind of reflection, it can know the singular, because, as we have said above(Q. 85, A. 7), even after abstracting the intelligible species, the intellect, in order tounderstand, needs to turn to the phantasms in which it understands the species, as is saidDe Anima iii. 7. Therefore it understands the universal directly through the intelligiblespecies, and indirectly the singular represented by the phantasm.71

68 Cf. Aristotle,De Anima, 429a22-24.69 Aquinas,Truth, vol. 2, p. 28, q. 10, art. 6.70 Ibid., p. 29, ad 7.71 Aquinas,Summa Theologica, vol. 1, pp. 440f., I, q. 86, art. 1.


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This conversio ad phantasmata, or turning to the phantasms, is therefore necessary

for our knowledge of singulars. It is something we are not conscious of, but Aquinas

mentions that we can see for ourselves how we turn to singulars again and again by

noting that it is easier for us to understand something when we are given concrete exam-

ples rather than arguing totally in the abstract.72 This is somewhat analogous to how the

intellect turns again to the phantasms to know singulars, albeit indirectly.

This, then, is how empirical knowledge works in the Aristotelian-Thomistic tradition.

The knower who thus possesses the intelligible species is said to know the object. In

knowledge, knower and thing known are identical; the knower becomes the object of

knowledge, but he does so in an intentional manner. This is why Aristotle says that

knowledge in act is the same as the thing itself.73 The scholastics called this mode of

existence intentional to distinguish it from natural or entitative existence, which is

existence in reality apart from being known. Intentional existence74 is peculiar to knowl-

edge and only denotes existence of objects as known. Interestingly enough, during the

modern era of Descartes and his intellectual heirs, the doctrine of intentionality was com-

pletely abandoned, and it was not until the 19th century that it was revived by Franz

Brentano, who heavily influenced Edmund Husserl and various schools of phenomenol-

ogy that remain influential to the present day.

72 Ibid., p. 429, q. 84, art. 7.73 Aristotle, De Anima, 430a19.74 This has alternatively been called intentional inexistence, inasmuch as it is existenceinthe knower.See Herbert Spiegelberg, Der Begriff der Intentionalitt in der Scholastik, bei Brentano und bei Husserl,Philosophische Hefte5 (1936): p. 85.


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6. KNOWLEDGE & EXISTENCE

Finally, we must touch upon the question of knowledge of the existence of sensible

things in the Aristotelian-Thomistic paradigm, especially because this is the kind of

knowledge denied or at least attacked by the radical skeptics. Strictly speaking, the exis-

tence of anything is not an object of knowledge because it is nothing concrete and cannot

be conceptualized. Existence is affirmed or denied in a judgment, which is the second

operation of the intellect. Since concrete existence is always existence of a singular, such

existence can only be discerned by the senses, and then only implicitly. It is necessarily

implicit because discernment of concrete existence comes by way of inference. The

senses perceive a concrete singular because it exists. If it did not exist, the senses could

not perceive it. The reality of sense-perception guarantees that the perceived object in fact

exists, since no one can perceive what is not actually there;75 at best, one can dream or

hallucinate it.76

The intellect itself gets a glimpse of existence when turning to the phantasm, because,

as we said before, the phantasm presents the sensed object in its concrete singularity, and

hence existence is implied. But since even the senses know existence only implicitly and

the intellect knows the singular only indirectly, we have to conclude that the intellect

only has indirectly implicit knowledge of concrete existence. Since, as we saw, the

proper object of the intellect is the universal, and since the universal is never concrete,

the intellect cannot know concrete existence directly.

Keeping all of these things in mind, we are now ready to look critically at the chal-

lenge posed by the idealists, a challenge that basically began with Descartes hyperbolic

75 Cf. the quote by Mortimer Adler in chapter 5.76 For a response to anti-realist arguments from the possibility of dreaming and hallucinating, see Part IV ofthis paper.


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doubt, the doubt which he himself had invented to free himself forever from skepticism,

but which he was really unable to overcome despite his confidence to the contrary.


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IV. RESPONDING TO THE SKEPTICAL CHALLENGE

St. Thomas took direct realism for granted. However valid thatrealistic position is, we cannot do that today. Both Neo-Thomism andmodern philosophy in general need an epistemology that vindicates

direct realism and rejects both rationalism and empiricism.

Robert J . Henle, S.J .77

As the foregoing section showed, the Aristotelian-Thomistic tradition teaches a direct

realism in epistemology. It is precisely this approach to knowledge that is heavily under

attack today, but it is certain to the present writer that no other approach can satisfy the

human mind inquiring into the nature of the workings of human knowledge, because it

alone is true. Since St. Thomas Aquinas did not have to battle with the issues and ques-

tions that were raised when Descartes set his axe to the tree of knowledge, we cannot

easily find the answers Thomas himself would have given to Descartes if he had lived in

the seventeenth century. Nevertheless, we have a solid foundation in the Aristotelian-

Thomistic tradition from which we can draw to evaluate the critical problem and answer

directly the challenges put forth by todays radical skeptics.

It is certain, says Jacques Maritain (1882-1973), that today reason can work use-

fully at the general reform everyone feels so necessary only if it first of all cures itself of

Cartesian errors.78 The Cartesian errors are numerous, of course, but the most funda-

mental of them is Descartes irrational desire for absolute certainty, which has driven

modernity into this vicious predicament of never-ending skepticism, to which all of the

post-Cartesian philosophies are a response in one way or another.

77 Robert J. Henle, AproposofFromUnity to Pluralismby Gerald McCool, S.J ., in John F. X. Knasas,ed.,Thomistic Papers VI (Houston, TX: Center for Thomistic Studies, 1994), p. 148.78 Jacques Maritain,The Dreamof Descartes, trans. Mabelle L. Andison (New York, NY: PhilosophicalLibrary, 1944), p. 10.


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Opening his Posterior Analytics, Aristotle writes: All teaching and all intellectual

learning come about from already existing knowledge.79 When Descartes, however,

began his critique of knowledge by tearing down, as it were, the house of knowledge,

doubting anything he was logically able to doubt, he prided himself on investigating the

foundations of knowledge without presuppositions of any kind. Presuppositionless phi-

losophy came to be an object of desire in modernity, and it is still very much taken to be

a high ideal in certain circles today. That, however, is precisely a grave error in Cartesian

philosophy: the attempt to presuppose nothing.

7. PRESUPPOSITIONS AND THEIR JUSTIFICATION

The reason it is erroneous to try to have absolutely no presuppositions or assumptions

whatsoever is that it is not possible. Moreover, it is not necessary. It is not possible

because human intellection would be without foundation and therefore could not operate

if there was nothing whatsoever that grounds and guides intellectual judgment. Even if

someone were to try as hard as possible to presuppose nothing at all and as a result would

remain entirely idle and not do anything, his inaction would still betray his holding to

some assumed premises or principles, because he would be judging that it is better to

remain idle than to do anything if one assumes nothing, and this judgment is a conclusion

that has come about as the result of an inferential chain. But every conclusion is based on

premises, which are necessarily presupposed.80 So, the fact that he makes the judgment to

79 Aristotle, Posterior Analytics, 71a1-2. Translation taken from Aristotle,The Complete Works ofAristotle: The Revised Oxford Translation, ed. Jonathan Barnes, vol. 1 (Princeton, NJ: Princeton UniversityPress, 1984), pp. 114-66.80 They may not be presupposed immediately but simply be other conclusions of previous chains ofreasoning; but ultimately, some premises must be accepted without proof, or else one would not be able toargue foror even believeanything. See also the discussion on self-evidence below.


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be idle reveals that he holds to some presupposed premises, or else he could not judge

that he should be idleand a judgment hemust make, one way or another, namely, the

judgment of whether to be idle or not. It is akin to the choice of not choosing.

Seeing that it is impossible to be totally presuppositionless, we need not panic,

however, for it is simply not necessary to start philosophical inquiry without any

assumptions whatsoever.81 The reason for this is that presupposing certain things is not an

obstacle to sound philosophical reasoningwhat is an obstacle is presupposing the

wrong things. If we assume dubious contentions, half-truths, or downright errors, then

philosophical inquiry will be inhibited, and we will most probably end up with a false

conclusion.82 Thus, rather than purging our intellects of all presuppositions indiscrimi-

nately, we ought to take care to eradicate only any falseor unjustifiable presuppositions

we might have.

In order to be able to distinguish true presuppositions from false ones, we must first

understand the nature and necessity of first principles. The necessity of first principles

arises out of the fact that all reasoning needs a foundation: [I]f it were necessary to

prove every statement, an infinite series of reasons would be required.83 This should be

obvious not only to the realist but also to the idealist. If the idealist wishes to deny this

foundationalism, he can only do so by giving reasons for his denialand this would in-

volve him in giving tacit approval to the very foundationalism he denies. He would thus

be trapped in a vicious circle. This shows that anyone who argues against foundation-

81 In fact, one may wonder whether the idealists conviction that it is necessary to start without anypresuppositions is a presupposition in itself.82 An example of this would be Jean-Paul Sartres argument for the non-existence of God. Sartre claimedthe notion of God was self-contradictory, but his argument is ultimately based on the unjustifiedandfalseassumption that consciousness is not-being. See Frederick Copleston,A History of Philosophy, vol.9 (New York, NY : Doubleday, 1994), p. 364.83 T.V. Fleming, Foundations of Philosophy(London: Shakespeare Head, 1949), p. 13.


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alism does so by using arguments that, if they are to be forceful at all, presuppose its

truth. Thus we can see the necessity for a foundation of all reasoning, and this basis is

provided in first principles and certain axioms and postulates84 that are self-evident.

For our purposes, we need to enumerate only two of the first principles, namely, the

principle of non-contradiction and the principle of identity. [T]he firmest [i.e., most

certain] of all principles, says Aristotle, is that about which it is impossible to make a

mistake,85 and that is the principle of non-contradiction. It states that the same attribute

cannot both belong and not belong to the same subject at the same time and in the same

respect. . . .

86

On this, all other principles depend.

87

An easier way of putting it is that

nothing can be and not-be at the same time in the same sense. Everyone believes this,

even if he denies it in his speech.88 In fact, his speech already betrays him, for he can

only speak against the principle of non-contradiction if the words he uses have the

intended meaning and not the opposite, and so he who claims he denies the principle of

non-contradiction could never speak against it. In fact, he could not even be silent, for

even understanding what is meant by the principle of non-contradiction presupposes its

truth. This is what Aristotle means when he says that he who destroys reason upholds

reason.89 It is really and truly impossible to deny this fundamental principle of all being

and thought.

84

Though we need not treat of them here, a number of self-evident axioms and postulates are provided,explained, and defended in Fleming,Foundations of Philosophy, pp. 13-20, 22-25.85 Aristotle, Metaphysics, 1005b11-12.86 Ibid., 1005b19-20.87 See Aquinas,Summa Theologica, vol. 2, p. 1009, I-II, q. 94, art. 2.88 Even in Aristotles times, people tried to deny this principle in their speech. But, Aristotle observed,what a man says he does not necessarily accept (Metaphysics, 1005b25-26), and this is especially sowhen his actions contradict what he professes to believe, as is the case with anyone who claims to reject theprinciple of non-contradiction.89 Aristotle, Metaphysics, 1006a26.


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The principle which follows from that of non-contradiction is the principle of iden-

tity, which simply says that a thing is what it is, that everything is identical to itself. In

mathematical terms it is simply the necessary truth that A =A. It would be literally

absurd to deny this, and it would also be impossible, for to deny it one must understand it,

and if it were not true, it could not be understood, for then it would not be what it is but it

would either be nothing at all or whatever anyone might want it to be. Like the principle

of non-contradiction, it is therefore likewise impossible to deny the principle of identity.

These two principles are first because they cannot be positively demonstrated,90 and

this is so because there is nothing more basic from which these principles could be

deduced. It would be entirely wrong, however, to think that simply because these princi-

ples allow of no demonstration, therefore we merely assume them, if by assume we

mean a sort of arbitrary adhesion in which we might as well not engage. First princi-

pleswhich, with Bittle, we may simply wish to call primary truths91, though not

demonstrable, are nevertheless not without any verification or proof. This is so because it

is false to think that unless something is demonstrable, it is believed only arbitrarily and

unwarrantedly. As Bittle points out:

We must remember . . . that only those truths demand a demonstration which are soobscure in themselves or so doubtful to our mind that we need another and clearer idea tomanifest them to us. If they are perfectly clear and self-evident, we do not need ademonstration to make them clear, because the very purpose of a demonstration isalready fulfilled. Under such circumstances, therefore, a truth would not be a gratuitousassumption nor anunwarranted presupposition. And that, precisely, is the case with the. . . primary truths: they need no demonstration, becausethey are self-evident.92

90 It is possible, however, to demonstrate the truth of these principlesnegatively, i.e., by reductio adabsurdum, showing that assuming the opposite leads to an impossibility, as we will do below.91 Bittle uses the term specifically to refer to the three undeniable truths of our own existence, the principleof non-contradiction, and the general reliability of our reason (see Bittle, Reality and the Mind, p. 67), butwe can nevertheless adopt this phrase and use it to refer to any indemonstrable, self-evident truth.92 Bittle,Reality and the Mind, pp. 69f.; italics given.


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We can see here that, ultimately, all inferential chains terminate in self-evident principles,

and this is exactly what the foundation of all knowledge is: self-evidence. St. Thomas

Aquinas concurs: [W]e naturally know some things as self-evident. We examine all

other things with reference to these, judging of them according to these.93 Self-evidence

is what provides the basis for any reasoning andmakes it possible.

The radical skeptic cannot deny this foundation, because in order to do it he must give

or at least have reasons for his denial, and these reasons are part of an inferential chain,

and they are thus based upon the very foundation the skeptic deniesor, to be more cor-

rect, the foundation heprofesses to deny, as it is impossible really to deny it. It is impos-

sible because his arguments have merit only if foundationalism is true, which amounts to

a contradiction because then he is right only if he is wrong. But he cannot hold to a con-

tradiction because the only way he could so is by saying that the principle of non-contra-

diction is false, an assertion which itself would be meaningless if the principle were false

and which would then be impossible to make, as we have seen. Therefore, it is false and

absurd to assert, as the skeptic does, that self-evident principles can and must be called

into question.

This can be further illustrated by T. V. Flemings following example:

To begin with, by seriously affirming I doubt everything, one implies that one knows(1) whatdoubt is, and (2) that doubtdiffers from knowledge and therefore (3) one knowswhat knowledge is. Further, the sceptic knows (4) themeaning of the proposition aboutwhich he doubts, and (5) the reasonwhy he doubts. Again, by suspending his judgmentabout the proposition under consideration, he knows (6) that the reasons put forward forit are insufficient to win his assent, and therefore (7) he knows what these reasons are.Finally, since he holds on to his scepticism lest he should fall into error, (8) he knowswhat error is, and (9) that he does not wish to err, and also (10) that he experiences adesirefor truth, etc. . . .94

93 Aquinas,Truth, vol. 2, p. 42, q. 10, art. 8.94 Fleming,Foundations of Philosophy, pp. 27f.; italics given. See also Bittle,Reality and the Mind, pp. 47-50.


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There is perhaps no better example than this that it is impossible to presuppose nothing

and to doubt everything. Of course it would be pure folly to seek to do what is impos-

sible. We see, therefore, that one of the errors of the Cartesian enterprise, from which

modern-day skepticism derives, was to seek to do the impossible. It should be of no sur-

prise, therefore, that it precipitated nothing but confusion in the form of a chaotic plu-

ralism.

We can see, then, that not everything can be questioned, not everything can be put

into doubt, as Descartes thought. Hence, it is not surprising that we should also find that

not everything can be demonstrated. The foundation upon which all demonstration is

based, and without which it would be impossible, 95 are the primary truths, which are self-

evident, because they are such that, as soon as the mind understands them, it necessarily

gives its assent. They are not, as Plato thought, innate to the mind, as the mind begins

as atabula rasa, a sheet of paper on which no word is yet written,96 which is simply the

default position of the passive intellect unless and until actualized. Self-evidence, thus,

is the ultimate criterion of truth, not Descartes clear and distinct ideas.97

It is clear, therefore, that first principles are self-evident and necessarily true. We can

and must admit of them before we can engage in any rational exercise, but by this we are

not simply assuming them, as though we arbitrarily decided to accept them without

foundation. As we have seen, the truth of these first principles cannot bedemonstrated,

but it can nevertheless bejustified. The first principles are presuppositions which cannot

be false and therefore can and must be presupposed for any philosophical inquiry.

95 Aristotle realized this centuries ago: It is not possible to understand through demonstration if we are notaware of the primitive, immediate, principles (Posterior Analytics, 99b20-21).96 Aquinas,Commentary on Aristotles De Anima, p. 217, III, lectio9, no. 722.97 See Descartes, Meditations, III, p. 24.


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Lest anyone accuse us of presupposing a gratuitous notion of truth, however, we must

now briefly turn to the nature and meaning of truth. It would be fair to assert, however,

that, at least implicitly, everyone knows what is meant by truth and everyone agrees on

the definition of the term, since people talk about what is true and false all the time. In

fact, simply by offeringa definition of truth, we already presuppose that we know what

we mean by the term to be defined, as we tacitly claim that our definition is in fact true.

This only poses a problem, however, to the one who would deny the traditional definition

of truth, which is simply conformity of the mind to the thing,98 as Bittle puts it, based

on Isaac Israelis definition endorsed by Aquinas.

99

This really means only that my judg-

ment is true if and only if what it expresses corresponds to the way things are in reality.

This is why Aristotle says that to say that what is, is, or that what is not, is not, is

true.100

This is, of course, a definition entirely in agreement with common sense, something

no one would contest, except, perhaps, a sophist masquerading as a philosopher. In fact,

as pointed out above, any disagreement with this definition must presuppose its veracity

in order to be meaningful. Thus, the skeptic cannot argue that the epistemological realist

is only presupposing his definition of truth to be correct without demonstrating it

since any requested demonstration would necessarily rely on that very definition under

dispute. We can say, therefore, that it cannot be denied without self-contradiction that

truth is conformity of the mind to things and that its ultimate criterion is self-evidence.

98 Bittle,Reality and the Mind, p. 19; italics deleted. Diametrically opposed to this traditional definition wasKants notion of truth, which we may candidly define as conformity of the thing to the mind.99 See Aquinas,Truth, vol. 1, p. 7, q. 1, art. 1. There are two other definitions of truth which St. Thomasgives in this article, but they need not concern us here.100 Aristotle, Metaphysics, 1011b27.


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8. THE REPRESENTATIVE THEORY OF PERCEPTION

With all of this in mind now, we are well equipped to answer the skeptical attacks on

the possibility and justification of knowledge. By faithfully applying the principles,

notions, and doctrines expounded by the Aristotelian-Thomistic tradition, as well as using

common sense, we can now counter the arguments brought forth against epistemological

realism since the time of Descartes.

When we look closely at Descartes own words, we see that as soon as he sets his

methodic doubt in motion, he does so on the basis of the representative theory of percep-

tion: I shall think that the sky, the air, the earth, colours, shapes, sounds and all external

things are merely the delusions of dreams which [some malicious demon] has devised to

ensnare my judgment.101 The experience we have of the external world is here tacitly

relegated to a knowledge not of the world but of mere images, i.e., representations, of

this world, as though we were sitting in a theater, directly aware only of the movements

on the screen in front of us. Descartes seems to accept this representational theory merely

on the grounds that he has found himself to have believed to be perceiving something

when in fact he was only sleeping: How often, asleep at night, am I convinced of just

such familiar eventsthat I am here in my dressing-gown, sitting by the firewhen in

fact I am lying undressed in bed!102

Interestingly enough, the only proof that is ever offered for the representative

theory of perception is negative in natureits truth is inferred from apparent diffi-

culties that are encountered with epistemological realism. If this is really all the repre-

sentationalist has to offer, then it follows that if realism can explain and properly account

101 Descartes, Meditations, I, p. 15.102 Ibid., p. 13.


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for these apparent difficulties, as we will show below, then the grounds for the represen-

tational theory are undermined. Of course, this is entirely crucial because the validity of

the critique of knowledge and radical skepticism depends upon this very theory to a large

extent.

A good way to start, then, is by first rebutting this representative theory of perception.

We can do so by appealing to the fact that there are no justifiable grounds to believe in

the theory in the first place and by answering the objections to realism that representa-

tionalists bring up, as we shall do in the next section; as well as by showing that even if it

were true, we could not know it. Since the representationalist cannot simply assert the

truth of the theory without any proof,103 it will suffice to show that even ifit were true, we

could not know it. This we will do as follows:

If we say that the ideas in our minds are accurate representations of the world outside

our minds, then this position is necessarily arbitrary, because it is entirely impossible to

verify that the representations in our minds are indeed true compared to the world out-

side. Just like a man who has only seen paintings of a relative of his does not know

whether the paintings are accurate renditions of the actual personhe simply assumes

itso we could never verify whether the ideas in our minds correspond to the external

world, as this world is only accessible through those very ideas. We are thus stuck in a

circle and can only arbitrarily assume or hope that these representations are truebut

we could never know it. Hence, any claim that this theory is true is a gratuitous guess at

bestand it can therefore be reasonably dismissed.

103 This is so becausequod gratis affirmatur, gratis negaturwhat is gratuitously asserted can begratuitously denied. Cf. the quote by George Mivart on page 52.


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John Locke was one of the foremost proponents of the representative theory of per-

ception, and he invoked the notion of causality to explain how it is that our ideas could

accurately represent external reality:

It is . . . the actual receiving of ideas from without [i.e., outside] that gives us notice ofthe existence of other things, and makes us know that something doth exist at that timewithout us which causes that idea in us. . . .104

In other words, the things outside the mind somehow cause these representational ideas in

us. But here the unspokenthough absolutely crucialpremise is that effects necessarily

resemble their causes, so much so that the caused ideas are an exact representation of

their cause, the thing.

But is this so? It could be so, but there is no necessity for it to be so, and this is what

is required in order for the theory to work. Some effects resemble their causes (e.g., a

baby resembles mother and father), but somedo not (e.g., a cake does not resemble the

woman who made it). It is plainly false, then, that all effects resemble their causes.105

Given this, however, we have no way of knowing whether the things outside the mind

produce effects which not only resemble them but in fact reproduce them with total accu-

racy. Again we see that representationalism is without justification and hence arbitrary.

Another unjustified and absolutely crucial presupposition the representative theory of

perception makes is that man has immediate, unrestricted access to his mind. It is with

good reason that the Aristotelian-Thomistic tradition differs with this view, as it is clearly

false according to the testimony of our experience. Children, though they are too young

still to engage in self-reflection, nevertheless know and interact with the world, which

they clearly perceive as outside of themselves. As soon as they are mature enough to

104 Locke, Essay, IV:XI.2, p. 537.105 Cf. Bittle, Reality and the Mind, pp. 188f.


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reflect on their own knowledge, however, they can know not only things in the world but

also the fact that they knowthose things; i.e., they can know their intellect.

This shows that reflection on the process of knowledge and the intellect and its con-

tents does not occur until we have actual knowledge of things. This is so because the

intellect is entirely passive until actualized in the process of knowledge:

Everything is knowable so far as it is in act, and not, so far as it is in potentiality. . . .[Therefore,] the intellect, so far as it knows material things, does not know save what isin act. . . . Now the human intellect is only a potentiality in the genus of intelligiblebeings, just as primary matter is a potentiality as regards sensible beings; and hence it iscalled possible [=passive]. Therefore in its essence the human mind is potentiallyunderstanding. Hence it has in itself the power to understand, but not to be understood,except as it is made actual. But as in this life our intellect has material and sensible thingsfor its proper natural object, . . . it understands itself according as it is made actual by the

species abstracted from sensible things, through the light of the active intellect, which notonly actuates the intelligible things themselves, but also, by their instrumentality, actuatesthe passive intellect. Therefore the intellect knows itself not by its essence, but by itsact.106

In other words, it is in and through the act of knowing something that the mind becomes

aware of its capacity to know.107 Our experience bears this out, and everyone can verify

it for himself. First there is always knowledge ofthings, i.e., extra-mental being, and it is

only after we have that, that we can reflect on the process of knowledge; and only then

can people come up with different epistemological theories, like the representative theory

of perception. As Maritain says: Realism is lived by the intellect before being recog-

nized by it.108 The rub for representationalists is that if we directly and immediately

knew only the contents of our own minds, then we would experienceourselves as doing

just that at first, and we would admit of the existence of extra-mental reality only as a sort

of reasonable inference that is drawn some time later. But this is obviously not the

106 Aquinas,Summa Theologica, vol.1, p. 444, I, q. 87, art. 1.107 Copleston, A History of Philosophy, vol. 9, p. 262.108 Jacques Maritain,The Degrees of Knowledge, trans. Gerald B. Phelan (Notre Dame, IN: University ofNotre Dame Press, 1995), p. 83.


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case. In fact, unless we first thought about things, we could not have reflective knowl-

edge, since there would be nothing to reflect on: The first thing thought about is being

independent of the mind.109 Author Christopher Derrick says as much: The prime ob-

ject of the intellect is reality, not ideas about reality.110 For the idealist, on the other

hand, it is an axiom that all thought is always about thought. Our experience, however,

does not confirm this assumptionon the contrary.

The modern skeptic faces an even more difficult challenge, for he has to realize that

unless we had knowledge ofthings, he couldnt even begin to reason his way to the rep-

resentative theory of perception, because then he would not have the experience of

knowledge. We can see this more clearly when we consider that he asks us to start phi-

losophy by making

a double abstraction or removal from things as [we] find them prior to the act ofphilosophizing . . . The critical philosopher first abstracts this act of knowing from theman possessing the act. Secondly, this abstracted act of knowing turns about and finds itcan throw into doubt both the existence of the man who has the act of knowing and theexistence of the thing known in the act of knowing.111

This is entirely ironic because if it were not for both the knowing man and the thing

known, there would be no knowing at all, nothing the idealist could analyze and inves-

tigate. Paradoxically, starting philosophy with this double abstraction certainly does not

qualify as presuppositionless.

So, when Descartes decided that the intellect was simply a container closed in on

itself to which alone we have direct access, he was putting forth a novelty without justifi-

109 Ibid., p. 115.110 Christopher Derrick, Escape fromScepticism: Liberal Education as if Truth Mattered (San Francisco,CA: Ignatius Press, 2001), p. 89.111 Wilhelmsen, Mans Knowledge of Reality, pp. 26f.


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cation. This position is not corroborated by experience, and if it were true, we could not

know it, as pointed out above.

While the representative theory of perception may perhaps seem plausible to some at

least prima facie, this plausibility diminishes as soon as we consider cases that involve

any of the senses other than sight. When I perceive solid ground under my feet as I walk

through the field, am I supposed to believe that what I am directly aware of is not the

solid ground but merely some representation thereof? We can all fathom a visual repre-

sentation, but what about tactile images? What about auditory, gustatory, and olfactory

images? What are those? How much sense does it make to say that when I taste some-

thing, I dont actually taste the thing but only its representation? Theprima facieplausi-

bility of the representative theory of perception depends entirely on the sense of sight.

But it is entirely reasonable to concludeand entirely unreasonable to deny, at least

absent any evidencethat just as the senses of touch, smell, taste, and hearing put us in

touch with the things themselves, so does the sense of sight.

Despite these problems, the representative theory of perception has enjoyed a lot of

popularity. We must therefore look at some of the objections broached against realism

that have been used to justify the representational theory.

9. OF DREAMS AND ILLUSIONS

In his First Meditation, Ren Descartes tells us what sets him onto this course of

hyperbolical doubt, namely, the possibility of sensory illusions and dreams:

Whatever I have up till now accepted as most true I have acquired either from the sensesor through the senses. But from time to time I have found that the senses deceive me, andit is prudent never to trust completely those who have deceived us even once. []

How often, asleep at night, am I convinced of just such familiar eventsthat I amhere in my dressing-gown, sitting by the firewhen in fact I am lying undressed in bed!


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. . . I see plainly that there are never any sure signs by means of which being awake canbe distinguished from being asleep.112

In short, Descartes asks: The senses have de

derkesen thesis against scepticism

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