A Brief and Incomplete A Brief and Incomplete History of theHistory of the

Philosophy of SciencePhilosophy of Science

Based largely on John Losee (1993) A Historical Introduction to the Philosophy of Science. Oxford: Oxford UP.

Plato Plato (427 - 347 BCE)(427 - 347 BCE)

• Plato’s epistemology denigrated scientific knowledge (knowledge of natural and material regularities)—such knowledge was not of the true reality, but merely of “shadows in the cave”

• Most important for Plato was knowledge of the Forms, the abstract entities which define the moral and metaphysical structure of the universe

• Knowledge of the Forms was to be gained not via observation and inference, but through pure reason and philosophical discourse

Inductive-Deductive Model:

From observations one proceeds by inductive inference (1) to General Principles which explain the observations in virtue of the fact that those same observations can be deduced (2) from the principles

AristotleAristotle (384-322 BCE)(384-322 BCE)

(1) Induction Deduction (2)

General Principles

Observed Phenomena

Aristotle’s I-D ModelAristotle’s I-D Model• Induction: enumeration, direct intuition

• Deduction: categorical logic

• Aristotle required that the General Principles be at least as evident as the observations—ultimately, they should be self-evident or necessary truths– The motivation here is to avoid arriving at claims which

describe only accidental regularities

– Rather GPs should be self-evident necessary truths reflecting the essences of objects and relations in nature

• This is related to the issue of the nature of laws

– The problem is that it is hard to see how we can get to necessary truths via induction

• This can be seen as an outcropping of the problem of induction

Aristotle’s Four CausesAristotle’s Four Causes• Material Cause: substance which undergoes a process

• Formal Cause: general conditions required for, and pattern or form of, process

• Efficient Cause: immediate conditions which precipitate the process or bring the object into being

• Final Cause: the purpose or end for which the process occurs—x occurs in order that… this sort of explanation is called teleological

– To fully explain a phenomena, each of its four causes must be explained

– Whereas now we focus primarily on a combination of the first three and often try to eliminate teleological explanation, Aristotle saw the final cause/teleological explanation as most important to understanding the nature of things

• this raises the issue of the nature of laws and causation

PythagoreanismPythagoreanism

• Pythagoreans revered numbers and mathematical relations to the point of mysticism

• The real is the mathematical patterns and harmonies discoverable in nature

• Describe the mathematical structure of a phenomena and you have knowledge of its essence

• This contrasts with Aristotelianism in that it focuses on the formal cause to the exclusion of the others, it especially neglects final causes

• Our current mathematical physics is, indeed, quite Pythagorean

• Pythagoreanism resembles Platonism in that it gives pride of place to abstract entities (numbers) and their relations, but it does not have much to say about moral Forms

Pythagoreanism—Problems…Pythagoreanism—Problems…• Given their knowledge of the Pythagorean Theorem, and

the fact that they conceived of all numbers as ratios, certain quantities were thought to be mysterious and incommensurable (immeasurable or unable to be compared with known quantities, what we would call the irrational numbers), e.g.,

• Of course, any good mysticism has to have mysteries…

• A further problem is that the same phenomena can be described by various different, but observationally equivalent, mathematical models

• This is the issue of underdetermination of theory by evidence

• This puts in question the ideal that mathematical description gets at the true nature of things…

Pythagoreanism and Saving Pythagoreanism and Saving AppearancesAppearances

• The tension between Pythagoreanism and the possibility of observationally equivalent mathematical descriptions was especially acute in astronomy

• It was well known—e.g., by Ptolemy(100-178)—that motion of the planetscould be equally well accounted for byvarious mathematical models

• The question then becomes whetherto view mathematical description asrevealing underlying nature or as merely providing a convenient description of the observable phenomena (saving the appearances)– This leads to the issue of the observation/theory

distinction and realism/anti-realism

E

E E

Three Models of Planetary MotionThree Models of Planetary Motion

Planet P revolves around point c, while c revolves around Earth, E

When P passes through a and b, P will appear to move backwards against the night sky seen from E (retrograde motion of P)

Planet P revolves around point c, while c revolves around Earth, E

When c and P are on opposite sides of E retrograde motion of P occurs

c

a b

P

P

Epicycle/Deferent Moving Eccentric

P

Heliocentric Circles

S

Planet P and Earth, E, both revolve around Sun, S

When E passes P retrograde motion of P occurs

These models also account for variations in speed and distance relative to E. Further epicycles, eccentrics, deferents, and equants can be added for greater precision. Of course, none of these is correct…

epicycle

deferent

eccentric

c

Saving AppearancesSaving Appearances• Especially in astronomy, a tradition evolved of

not claiming reality for the mathematical models—the task for the astronomer is not to hypothesize about the unobservable nature of things, but to provide convenient and observationally adequate models

• This is a form of anti-realism

• Relates to the observation/theory distinction

• This is very similar to naive positivism, operationalism, and current constructive empiricism

• Ptolemy was inconsistent on this issue, usually stressing Pythagorean realism, but sometimes weakening his claims to saving the appearances (though he never considered heliocentrism plausible)

Saving Appearances…Saving Appearances…and Oneselfand Oneself

• The famous heliocentrists, Copernicus (1473-1543), Galileo (1564-1642), and Kepler (1571-1630), each had Pythagorean commitments– each held to the reality of his model, and– each was strongly motivated, not just by data and

observation, but also by strong mathematical aesthetics, a desire to find certain kinds of harmonies in nature

• This raises the issues of scientific revolutions and the rationality of theory change

• Yet each of the heliocentrists was advised to present his work as a mere saving of appearances to avoid persecution from the Church. Galileo did not take great pains to hide his commitment to the reality of heliocentrism. As a result, Galileo was brought before the Inquisition and forced to recant, spending the his last eight years under house arrest.

• Again, the issues of rationality, revolutions, and social forces

Copernicus

Galileo

Kepler

AtomismAtomism• A further metaphysical/explanatory picture that can be

contrasted to Pythagoreanism and Aristotelianism is Atomism

• Proponents included Leucippus (490-430 BCE) and Democritus (460-360 BCE)

• The general approach was to explain observed qualitative and quantitative changes by reference to quantitative changes at a more elementary level of organization

• This, too, neglects the Final Cause, and is thoroughly materialistic, thus it is antithetical both to Aristotelianism and to Platonism/Pythagoreanism

• One difficulty is to avoid simply attributing to the atoms the very property to be explained at the macro level. Doing so would create a circular “explanation”, which is to say, no explanation at all (e.g., day-old coffee is bitter because it has acquired large numbers of bitter atoms)

• This raises the issue of the nature and quality of scientific explanation as well as the observation/theory distinction

Development of the I-D model Development of the I-D model in the Middle Agesin the Middle Ages

• The Middle Ages saw a number of modifications to and developments of Aristotle’s basic I-D model…

Robert Grosseteste Robert Grosseteste (c. 1168-1253)(c. 1168-1253)

• Attempted to systematize choice among competing theories

– Use Modus Tollens to eliminate all but one possible hypothesis

– I.e., deduce a consequence, C, from a hypothesis, H, show that not-C, conclude not-H

– Modus Tollens:If H, then Cnot-Cnot-H

– Problem is, this cannot be done;it is not possible to eliminate allbut one hypothesis

• underdetermination

Roger BaconRoger Bacon (1214-92)(1214-92)

• Three Prerogatives of Experimental Science:

1. From general principles deduce claims about new phenomena, and put these to experimental test (Aristotle required only that the original phenomena be deduced)

2. Actively and systematically experiment in order to increase data and knowledge of phenomena

3. Use this knowledge to develop new techniques for gathering data and testing hypotheses, as well as for developing practical tools and new crafts; look to old craft traditions as a source of data and technical knowledge

• These constitute advances over Aristotle’s simple inductive-deductive method, because it stresses systematic gathering of data, the extension of implications and tests to new phenomena, and a bridging of the gap between intellectual knowledge and craft knowledge

Scotus and Ockham on InductionScotus and Ockham on Induction

• Further forms of induction articulated

– These two methods are often called the (first two) of Mill’s Methods, after J.S. Mill (1806-73), whose arguments in favor of inductivism were widely influential.

Duns Scotus(1265-1308)

Method of Agreement

Case Circumstances Effect Conclusion

1 ABCD e

A can be the cause of e2 ACE e

3 ABEF e

4 ACD e

William of Ockham(1280-1349)

Method of DifferenceCase Circumstances Effect Conclusion

1 ABC eA can be the cause of e

2 BC -

Ockham’s RazorOckham’s Razor

• William of Ockham—Ockham’s Razor– A demand for simplicity, stated in various forms:

• Assume nature takes the simplest path available

• assume the minimum number of (types of) objects necessary to the theory/explanation

• do not unnecessarily complicate theory

• eliminate superfluous concepts.

• Ockham would not like the first formulation because it makes a metaphysical claim about nature (that it pursues the simplest path), and, Ockham would say, we cannot know how God has designed nature—God could complicate nature unnecessarily if he so chose

• Instead, Ockham cast his injunction so as to apply to our theories rather than to nature itself—keep the theories as simple as possible– while in principle God could complicate things, we should not pretend

to knowledge of God’s design

– we should make our theories as simple and tractable as possible, given the evidence

Necessary Truth of First PrinciplesNecessary Truth of First Principles• Note that Ockham’s caution in stating his razor, as well as the cautious form of the

conclusions in the two inductive methods above, point out a growing recognition of the fallibility of inductive inference, as well as a reconsideration of Aristotle’s requirement that the First (General) Principles be self-evident. For some thinkers self-evidence may still have been a goal, but many began to recognize (in theory if not in practice) that one had to be more cautious about the strength of one’s inductively generated conclusions.

• Duns Scotus believed that sense experience allowed us to recognize necessary truths, but that such truths were true in virtue of the meanings of the terms, and it was understanding of these meanings, not sense experience, which justifies our belief in them (see Herschel); such truths are necessary, as their denials are self-contradictory

– An early version of analyticity

• Aristotle, Scotus, and others had assumed that certain first principles of the special sciences could be known to be necessary, hence what counted as self-contradictory extended beyond just what could be reduced to a logical contradiction

• Nicolas of Autrecourt (c. 1300-1350+) had a much stricter notion of necessary truth, restricting it to claims whose denials are logical contradictions

– Much like David Hume (1711-1776) four centuries later, Nicolas concluded that we can have no certain knowledge of causal relations (Hume also draws stronger conclusions)

– Much unlike Hume, Nicolas used his critique to encourage faith in a Christian God

– The issue of laws and causation

Galileo and Francis BaconGalileo and Francis Bacon• Galileo (1564-1642) stresses the role of abstraction

and idealization in the inductive stage• Takes to heart and implements R. Bacon’s

injunction to test hypotheses against new phenomena

• Is a master of qualitative observation and experimental design

• And, of course, one of the first the use the telescope to make astronomical observations

• Francis Bacon (1561-1626) tries to develop a more systematic and more careful version of Aristotle’s I-D model– Eliminate all prejudices and assumptions– Gather a huge amount of data and generalize

cautiously– Build up to ultimate generalities through a hierarchy

of intermediate steps (restricted generalities)– Science should be an organized community endeavor– Science should have practical results, eventually man

should regain his dominion over nature

René DescartesRené Descartes (1596-1650)(1596-1650)

• Rejects Aristotelian I-D Model, and inverts F. Bacon’s ascent to generality

– Rather than inductively building from observations to successively more general and more fundamental truths (as F. Bacon), Descartes proposed to start with the most general and most certain truths and derive more specific knowledge and observations from those

– Clarity and distinctness a guide to a priori knowledge of concepts, their implications, and their application

• E.g., Descartes thought he could derive, a priori, laws of physical matter from metaphysical truths about extension and motion of bodies, and general truths about the relation between mind and body from truths about the different substances…

– Observation has a role in determining under which circumstances regularities occur, but observation cannot support general laws

Isaac Newton Isaac Newton (1642-1727)(1642-1727)

• Advances an I-D model and an Axiomatic Method– Method of Analysis and Synthesis; a form

of the I-D model, but also

– A three stage, non-inductive procedure1. Formulate an axiom system of definitions

and relations (e.g., his laws of motion)

2. Specify a procedure for correlating theorems deduced from the axioms with observable phenomena (i.e., interpret the axiom system; e.g., generalizations concerning planetary motion)

3. Attempt to confirm the observational implications of the system (e.g., specific predictions concerning planetary motion)

– Newton recognized a form of imaginative, abstractive, and idealizing induction in formulating the axiom system in stage 1

David Hume David Hume (1711-76)(1711-76)

• Broad empiricist attack on metaphysics and causal knowledge

– Criterion of meaningfulness • A thought is genuinely meaningful only if it can be

traced back its constituent sensory impressions– (similar to 20th c. positivism)

– Knowledge divided into…• Relations of ideas

– Their denials are logically contradictory, so theyare necessary truths, known with certainty

– Subject matter restricted to logic, math, geometry—no question of existence or causation is a relation of ideas (see analyticity)

• Matters of Fact– Neither a MOF nor its denial is logically contradictory,

so each is possible– Based in knowledge of cause and effect, which is not

certain… In fact,

David Hume David Hume (1711-76)(1711-76)

• Induction, Causation, Matters of Fact– Knowledge of MOF based in knowledge of cause and

effect

– Knowledge of cause and effect based on experience

– All knowledge based on experience presupposes the fundamental inductive principle that the future will be like the past

– But this principle is not a relation of ideas, so it must be a MOF…

– But then the fundamental principle of induction cannot be justified—any attempt to do so would require presupposing that very principle

• This is Hume’s version of the problem of induction

David Hume David Hume (1711-76)(1711-76)

• Hume concludes that our judgments concerning matters of fact (including causal relations) are not rationally grounded at all

• Rather there are (stronger or weaker) habits of expectation which evolve in us as a result of (i) our natural propensities and(ii) observation of constant conjunctions of events (fire then heat, fire then heat…)

• This “skeptical solution” is a form of psychological naturalism—description of what we do, how we cannot avoid it

• He is rejecting inductive justification (though not inductive practice), as well as intuition of necessary truth

• Indeed, we cannot know the “hidden springs and principles” underlying the world we observe, all we ever “know” of is the constant conjunctions of kinds of events—laws and causation

• Except, perhaps, for Nicolas of Autrecourt, Hume is the first we’ve looked at to completely reject the ideal of somehow arriving at secure generalizations or certain First Principles of some sort

• Hume, unlike Nicolas, used these skeptical results to argue against metaphysics and religion

Immanuel KantImmanuel Kant (1724-1804)(1724-1804)

• Kant responds to Hume by distinguishing the formfrom the content of knowledge

• Form is not given in experience; rather the “rawdata” of experience is structured in various waysby the rational human mind– Space and Time are the Forms of Sensory Intuition,

all perception is structured by these forms– Perceptions so structured are further organized and

synthesized according to 12 Categories ofUnderstanding (e.g., Unity, Substance, Causality, Contingency, etc.)

– Judgments are made and organized via the Regulative Principles of Reason

• Since the structures/forms Kant posits are inherent in the human rational mind, they are open to philosophical investigation, they can be known via pure reason

• Since any knowledge (esp., empirical/scientific) presupposes the Forms, Categories, and Principles, we can (contra Hume) have knowledge of the general features of any possible scientific theory, including fundamental and general truths about causation, matter, motion, etc.

Immanuel KantImmanuel Kant• Transcendental Idealism

from a point of view which attempts to transcend our forms of cognition, we recognize how much our mind and its structure contributes to our knowledge of the world

• Empirical Realismfrom a point of view which does not attempt the impossible transcendence, the structures imparted by the Forms, Categories, and Principles are fully real, and necessary truths regarding such things as causal relations and matter can be known

• Some problems with this ingenious and seductive picture:– What justifies saying “this is what any theory or cognition must

presuppose”? How can we be sure we’ve correctly identified the most basic forms, categories, and principles? Must they be unique? Kant thought he had identified unique basic forms, but some of what he took as basic to science has since been changed and rejected by science

– How can one coherently speak of the transcendental unreality of forms and categories, while maintaining that transcendence is impossible, and that the transcendental (noumenal) world is unknowable?

J.S. Mill J.S. Mill (1806-73)(1806-73)

• Laws, General Principles, and theoreticalclaims are justified by inferences fromexperience which satisfy inductive schemasor forms—this is known as Inductivism– Much like the I-D model, but little import

allowed to the D side, and Mill had veryspecific inductive methods in mind

• Mill a bit unrealistic about how wellinductive schemas can justify theoretical claims

• Deduction from hypotheses of successful prediction a requirement, but not a justifying factor unless all other possible hypotheses are eliminated

• Again, justification of theoretical claims is gained only by conformity of the data to inductive schemas supporting the theoretical claims…

Mill’s MethodsMill’s Methods

Method of Agreement* Method of Difference*

Method of Concomitant Variation

Case Circumstances Effect Conclusion

1 A·n BC a·n b (occurrence of a is varying proportionally to occurrence of A)

So either A causes a, or A and a have a common third cause

2 A·0 BC a·0 b

3 A·1/n BC a·1/n b

Method of Residues

Case Circumstances Effect Conclusion

1 ABC abc

A is the cause of a2 B b

3 C c

*See Scotus and Ockham on Induction

Hypothetico-DeductivismHypothetico-Deductivism• William Whewell (1794-1866) and

W.S. Jevons (1832-82) rejected Inductivism

• Rather than justified on the basis of inductions, a hypothesis is justified when it

– Is consistent with other established hypotheses, and

– The consequences deducible from the hypothesis agree with observations

• With its strong emphasis on predictive test, this is in the spirit of Aristotle, R. Bacon, Galileo, and Newton, but the view gives more priority to predictive test than these others (by giving much less importance to induction)

Whewell

Jevons

Herschel on Discovery and JustificationHerschel on Discovery and Justification

• John Herschel (1792-1871)• Herschel distinguished the issue of how a

theory was arrived at (context of discovery)from the issue of its acceptability orjustification (context of justification)

• He claimed that context of discovery isstrictly irrelevant to context of justification

• Discovery– Use of inductive schemas– Abstraction and imaginative hypothesis– F. Bacon-like hierarchy of generalizations

• Justification– Success of deduced predictions (thus a form of hypothetico-

deductivism), especially• Extension of predictions to extreme cases• Deduction of unexpected predictions and their successful testing• Use of “crucial experiments” to decide between competing

theories/hypotheses

Problem(s) of InductionProblem(s) of Induction• Two Issues:

– The Descriptive Issue: we arrive at beliefs regarding unobserved matters of fact (future particulars, eternal generalizations)—How do we do that?

– The Normative Issue: do we arrive at such beliefs the way in which we ought to arrive at them? I.e., are we justified in our practice? If not is there any practice we could adopt which is justified?

• Problems Regarding the Normative Issue:– Uncertainty/Underdetermination : Inductive inference is

underdetermined, hence not truth-preserving, hence some amount of uncertainty is involved, even when starting from certain premises

– Lack of Rational Ground: The basic principle(s) of induction are not logical truths, nor self-evident, so what justifies those principles? As Hume points out, we cannot appeal to experience, because any such appeal presupposes the very inductive principles in question—this is the problem

• A useful online discussion: The Problem of Induction

UnderdeterminationUnderdetermination• The Underdetermination of Theory by Evidence

• Given any amount of observational evidence, there will be more than one (indeed infinitely many) theories compatible with that evidence

• A unique theory is never dictated by the evidence, not even if we had all possible evidence

• This raises the question of how and if we can rationally decide between theories

• WRONG and often WRONGLY ATTRIBUTED TO W.V. Quine version: a theory can be preserved in the face of any contrary evidence (what Quine says, in case you’re interested, is that a hypothesis or statement can be preserved as long as others are given up, but this is a CHANGE IN THEORY, some hypotheses are preserved, others not)

– This correct understanding of Quine implies that

• There are no crucial experiments to rule out a hypothesis

• There are (near) crucial experiments to rule out whole theories

Observation/Theory Observation/Theory DistinctionDistinction

• Intuitively, there seems to be a distinction between that which we can observe—the observational; and that which we cannot observe—the theoretical– Observable: people, stars, trees, rocks, grains of sand, a patch of red…– Theoretical: electrons, quarks, viruses, dark matter, the big bang,

trees, people…• The theoretical is posited or inferred to help predict and explain

the observable• Problems abound for this distinction:

– Does the distinction concern observable vs. theoretical• Objects?• Words and Sentences involved in scientific claims?• Sense Data vs. Things in the World?

– How sharp is the distinction?• Does something projected onto the retina through a microscope or

telescope count as observable?• What about artificially colored images produced on a screen by an electron

microscope or an infrared sensitive telescope?• What about “observations” made by a prosthetically enhanced human?

Revolutions and RationalityRevolutions and Rationality

• Given the problems of Induction and Underdetermination, is theory acceptance (change) at all rational?

• If so, there must be some substantial constraints on theory acceptance beyond mere induction and deduction of observable consequences

• What are they? How do we know?

next slide…

Revolutions and RationalityRevolutions and Rationality• Kuhn claims that scientific revolutions (periods of significant

change in theory and practice) are highly non-rational affairs, highly unconstrained

• In part, this is because what makes a revolution revolutionary is that the normally accepted theories and the methodological practices they ground are in question and changing, hence, it seems, they cannot constrain their own change in a rational way

• But revolutions are lauded as important advances in our thinking and knowledge, and we think they are good and justified changes in theory—but how could they be if they are not rationally guided?

• Moreover, historians of science often recognize that many social forces can play a role in revolutions and the (non)acceptance of theory—what gives?

• Finally, the apparent lack of rational constraint and presence of social forces raise the demarcation issue—how, if at all, is science different from other organized bodies of beliefs (religion, metaphysics, political structures, cultural tradition)?

Social ForcesSocial Forces• How and to what extent do religious, cultural,

political, gender, racial biases and interests affect scientific theorizing?

• Can they be avoided? Ought they to be avoided?

• This has implications for the issue of the rationality of theory acceptance and change

• If theory acceptance and change are not rationally constrained there seems to be plenty of room for non-rational social forces to be in play

• Moreover, the apparent lack of rational constraint and the role of social forces raises the demarcation issue…

DemarcationDemarcation• How, if at all, is science different from other

organized bodies of beliefs (religion, metaphysics, political structures, cultural tradition)?

• How can a difference be marked out?

• Can “good” science be distinguished from “bad” science? Is “pseudoscience” a third thing, or just really bad “bad” science?

• Does/should science have a privileged epistemological standing in relation to these others?

• This all relevant to revolutions and rationality, and social forces

Realism/Anti-realismRealism/Anti-realism• Given the various epistemological difficulties (

underdetermination, problem of induction, rationality, social forces), and the lack of a consensus on these issues, why should we think that our theories are actually describing reality?

• The apparently large gap between observational and theoretical knowledge inspires worry about realism

• Metaphysical difficulties come into play here as well—we do not have good understandings of the nature of laws and causation, explanation, so how can we claim that we are discovering the nature of the universe?

Laws and CausationLaws and Causation• Laws are often thought of as general statements of causally

necessary connection between events, and the statements of laws themselves are sometimes thought to be necessary truths

• But given the various epistemological problems, especially the Humean critique, it is unclear whether or not causes and laws can be or be known to be as described above

• If laws do not state a necessary connection and are not themselves necessary truths, then what, if anything, distinguishes them from accidentally true generalizations?

• Is there really any such thing as a law of nature?

• This all connected to issues of realism and explanation

ExplanationExplanation

• Science is supposed to explain things to us…

• But what does it mean to have a scientific explanation?

• Does mere derivability of a description from more general truths constitute an explanation?

• What sort of explanations can science provide?

• How can we tell good from bad explanations?

AnalyticityAnalyticity• Statements which are analytic are supposed to be conceptual truths—true in virtue of

the meanings or concepts involved

– Locke: a part of a complex idea is predicated of the whole

– Kant: the predicate concept is contained in the subject concept

– Carnap: true in virtue of the meanings of the constituent terms

– E.g., ‘all bachelors are unmarried’

• This is contrasted with synthetic statements whose truth (or falsehood) is a matter of something beyond the meanings or concepts involved (the world, matters of fact)

– E.g., ‘all faculty are bachelors’

• Locke and Kant were the first to make use of this distinction, it played a prominent role for the logical positivists (as we’ll soon see), Quine repudiated it

• Analyticity provides a way (though not the only way) of explaining how at least some truths are

– Knowable a priori—without appeal to experience—via linguistic analysis or merely understanding the language

– General principles, or frameworks, for theorizing

– Necessarily true

– A matter of linguistic convention

– Accepted or rejected on purely pragmatic considerations and thus lack metaphysical import

it all depends on who is making the distinction and to what use they are putting it