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Main claim Three kinds of physicalism The argument for physicalism Objections against physicalism

Physicalism

Feb. 12–14, 2014

Physicalism Feb. 12–14, 2014


Overview I

Main claim

Three kinds of physicalism

The argument for physicalism

Objections against physicalismHempel’s dilemmaThe knowledge argumentAbsent or inverted qualia



Review

3 main theories in the philosophy of mind literature:1 Substance dualism — Plato, Descartes: there are two kinds of

substances: spiritual and physical (soul and body), and onecan exist without the other.

2 Physicalism — especially in the 20th century3 Hylomorphism — Aristotle, Middle Ages



Physicalism: Main Claim

Main Claim of Physicalism:Everything is physical; everything can be exhaustively describedand explained by physics.

A form of monism (= there is one kind of entities)Everything = every feature of every individual; all theindividual’s behavior. All the entities that exist are physicalentities — the fundamental physical particles or materials thatare described by physics.Exhaustively = the physical explanation leaves out nothing.



Implications of Physicalism

If physicalism is true. . .Persons, if they exist, are either fundamental physicalparticles, or else collections of fundamental physical particles.Their behavior can be exhaustively described and explained byphysics.A description of all positions and properties of all thefundamental physical particles that exist would provide acomplete description of everything — even though it nevermentioned the di�erence between living things and nonlivingones, or mental beings and nonmental ones.Thus, if there were a Super-physicist somewhere in theuniverse, who knew all but only the physical facts, he wouldknow everything.



Three Kinds of PhysicalismThey di�er in how they understand the relation of psychologicaldescriptions and explanations to physical ones.

1 Eliminative physicalism: Psychological descriptions are allfalse. In reality, there are no mental states; psychological talkis just gibberish.

Everyday talk about your feelings, desires is like talk about theGreek god Zeus when trying to predict the wheather.

2 Reductive physicalism: Some psychological descriptions aretrue: they directly correspond to physical descriptions. Mentalstates are really just physical states (e.g., states of the brain)

Your beliefs and desires have physical features.3 Non-reductive physicalism: Some psychological descriptions

are true, but they do not correspond directly to physicaldescriptions. Mental states are part of an abstract way ofdescribing physical states.

Psychological descriptions do not have real explanatory value.Physicalism Feb. 12–14, 2014


A few things to note:All physicalists agree that all things are physical (includingnon-reductive physicalists)This means that if you are a physicalist, there is no separaterealm of the mental (this why it is a monist theory, asopposed to a dualism)Do you have souls, according to the physicalist? — Well, itdepends which kind of physicalist you ask.

Eliminativist: No.Reductivist: Yes; it is physical, and you should talk about it inphysical terms.Non-Reductivist: Yes; it is physical. You can talk about it innon-physical terms, but that will not add to the entities youhave in physics.



Reduction vs. Non-Reduction

Reduction:The ability of one theory to take over the descriptive andexplanatory jobs of another theory. If Ta takes over the descriptiveand explanatory jobs of Tb, then Tb is reducible to Ta.

We use theories to describe and explain things — to performvarious descriptive and explanatory jobs.Sometimes in the course of scientific progress one theory takesover the descriptive and explanatory jobs of another theory.(E.g., Kepler’s laws of planetary motion were reduced toNewtonian mechanics; physical optics was reduced toelectromagnetic theory.)



Reduction vs. Non-ReductionWill ordinary psychological discourse be reduced to neuroscience?

Reductive physicalism: YES.

Caesar and the RubiconSuppose we use psychological discourse to explain why Caesarcrossed the Rubicon: “Caesar crossed the Rubicon because hewanted to maintain political power, and believed marching onRome the best means of maintaining it.” According to thereductive physicalist: “Wanting to maintain political power” =Brain State A; “Believing that marching on Rome is the bestmeans of securing political power” = Brain State B; “Crossing theRubicon” = Muscular Contractions C. Thus, we can replace ourexplanation with this one: Caesar was in Brain States A and B,and whenever these brain states occur, they typically causeMuscular Contractions C.



Reduction vs. Non-ReductionWill ordinary psychological discourse be reduced to neuroscience?

Nonreductive physicalism: NO.Psychological discourse satisfies special descriptive andexplanatory interests.Therefore, physics, chemistry, neuroscience, and otherbranches of science cannot take over the descriptive andexplanatory jobs we use psychological discourse to perform.

But note:Nonreductive physicalism is still a form of physicalism. It doesnot say that psychological discourse describes somethingnonphysical.When we describe things psychologically, we are just describingthem abstractly, using di�erent terms.Analogy: if we describe juniors and seniors as ‘upperclassmen’,we are not describing any entities in addition to the juniors andseniors. We are simply describing the junior and seniors using adi�erent term.



The Argument for Physicalism

Physicalists agree and take it for granted that science is our bestmeans to get to reality.

The Argument for Physicalism:P In the past, whenever people have tried to explain

things by appeal to nonphysical entities, thoseexplanations failed, and by contrast a physicalexplanation succeeded.

) Therefore, whenever people try to explain things byappeal to nonphysical entities, those explanations willfail, and by contrast physical explanations willsucceed.



The Argument for Physicalism

The form of the argument: InductiveJustification for the premise: Examples from the history ofscience.

Explaining magnetism non-physical spirits =∆ electromagneticforceExplaining the movements of the planets by non-physicalminds =∆ gravitational forceExplaining abnormal human behavior by non-physical demons=∆ abnormalities of the brain

In all of these cases, the failed nonphysical explanation wasreplaced by a successful physical one; thus, we have goodreason to think that nonphysical explanations will always fail,and that physical explanations will always succeed.


Main claim Three kinds of physicalism The argument for physicalism Objections against physicalismHempel’s dilemma The knowledge argument Absent or inverted qualia

Objections Against Physicalism

3 main objections:1 Hempel’s dilemma2 The knowledge argument3 The argument from absent or inverted qualia



Hempel’s Dilemma

Carl Gustav Hempel(1905–1997)

Philosopher of science,logical empiricismBorn in Germany; fled to theUS, taught at Yale,PrincetonInterested in philosophy ofmathematics, nature ofscientific explanationBest known for theHempel’s dilemma, and theRaven paradox



Hempel’s Dilemma

Hempel’s DilemmaP1 Physicalists must define physics either relative to a

preliminary stage of its development or relative to thefinal, ideal stage of its development.

P2 If physicalists define physics relative to a preliminarystage of its development, then physicalism is false.

P3 If physicalists define physics relative to the final, idealstage of its development, then physicalism is lackingin content (we do not even know what it is saying).

) Either physicalism is false, or else physicalism islacking in content.



Hempel’s Dilemma

Form of the argument: Destructive dilemma (valid)Justification for the premises:

P1: Sciences, including physics, develop in twostages: a preliminary stage when theories areadvanced, falsified, and replaced by moreaccurate theories, and a final, ideal stage whenthe most accurate, unrevisable theory has beenachieved. But if sciences progress in two stages,then physicalists must define ‘physics’ relative toone stage or the other. Therefore, physicalistsmust define physics either relative to apreliminary stage of its development or relativeto the final, ideal stage.



Hempel’s Dilemma

Justification for the premises:P2: If physicalists define physics relative to a

preliminary stage of its development, thenphysicalism is the claim that everything can beexhaustively described and explained by thatpreliminary stage of physics. But not everythingcan be exhaustively described and explained by apreliminary stage of physics (this is why it is apreliminary stage — it is partly false!).Therefore, physicalism is false.



Hempel’s Dilemma

Justification for the premises:P3: If physicalists define physics relative to the final,

ideal stage of its development, then physicalismis the claim that everything can be exhaustivelydescribed and explained by the final, ideal stageof physics. But we do not know what the final,ideal stage of physics says (we are not thereyet). Therefore, we do not know whatphysicalism says (the claim lacks content).



Hempel’s Dilemma

Hempel’s DilemmaP1 Physicalists must define physics either relative to a

preliminary stage of its development or relative to thefinal, ideal stage of its development.

P2 If physicalists define physics relative to a preliminarystage of its development, then physicalism is false.

P3 If physicalists define physics relative to the final, idealstage of its development, then physicalism is lackingin content (we do not even know what it is saying).

) Either physicalism is false, or else physicalism islacking in content.



Hempel’s Dilemma



The Knowledge Argument

A further argument against physicalism.

The Knowledge ArgumentP1 If physicalism is true, then all facts are physical facts.P2 But not all facts are physical facts.) Therefore, physicalism is false.

Form of the argument: Modus tollens (valid)Justification for the premises:

P1 : A fact is what corresponds to a proposition; ifeverything can be described by physics, thatmeans that all facts are physical facts.




Argument for P2:2i If it is possible to know all the physical facts without

knowing all the facts, then not all facts are physicalfacts.

2ii But is possible to know all the physical facts withoutknowing all the facts.

P2 Therefore, not all facts are physical facts.




But why accept 2ii?Conceivability-possibility principle: if I can imagine such acase (when someone knows all the physical facts, but not all

the facts), then it is possible.

Thought experiment for 2ii : Mary’s caseMary knows all the physical facts, yet she has never experiencedcolor. She learns a new fact when she experiences color for the firsttime (e.g., sees a ripe tomato). But, of course, it is not possiblefor someone to learn what he or she already knows. Thus, in thiscase, we imagined a case when Mary knew all the physical facts,yet there was something she did not know.



The Knowledge Argument — Summary

Mary’s example: we can imagine a case when someone knowsall physical facts and yet does not know all the facts. =∆(conceivability-possibility principle) =∆It is possible that someone knows all the physical facts andyet does not know all the facts. =∆Not all facts are physical facts. =∆Therefore, physicalism is false.



Absent or Inverted Qualia

Qualia = the subjective quality of experience; e.g., what it is

like to see red.

The Argument from Absent or Inverted QualiaP1 If it is possible that your physical replica has absent

or inverted qualia, then physicalism is false.P2 But it is possible that your physical replica has

absent or inverted qualia.) Therefore, physicalism is false.

Form of the argument: Modus ponens (valid)



Absent or Inverted QualiaJustification for P1:

1i If physicalism is true, then either (a) qualia do notexist, or (b) qualia are physical things.

1ii But qualia do exist (we know it from experience).1iii Therefore, if physicalism is true, qualia are physical

things. [From 1i , 1ii ]1iv If qualia are physical things, then your physical

replica could not have absent or inverted qualia.[From the definition of ‘physical replica’]

1v Therefore, if physicalism is true, then your physicalreplica could not have absent or inverted qualia.[From 1iii , 1iv ]

P1 If your physical replica could have absent or invertedqualia, then physicalism is false. [Contrapositionfrom 1v ]



Absent or Inverted Qualia

Justification for P2:Conceivability-possibility principle; I can imagine such asituation, therefore, it is possible.

Qualia Inverted qualia Absent qualiaPhysicalism Feb. 12–14, 2014


Absent or Inverted Qualia — Summary

I can imagine that my physical replica has absent qualiaTherefore, qualia cannot be physicalBut if physicalism is true, qualia are physicalTherefore, physicalism is false.


physicalism - weeblytothzit.weebly.com/.../1/0/6/7/10676184/0212_physicalism.pdf · 2018. 10....

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