Test 3

Minds and Bodies Review

The Questions

•  What am I? – What sort of thing am I?

•  Am I a mind that “occupies” a body? •  Are mind and matter different (sorts of)

things? •  Is conscious awareness a physical event or

something that happens in an immaterial soul?

How many kinds of “stuff?”

Dualism: Minds and

Matter

Descartes

Monism:

Idealism: Everything is mental

Berkeley

Materialism: Everything is

material

Eliminative Materialism

There are no mental states,

just like there are

no ghosts.

Graziano

Identity Theory

Mental states are

identical to brain

states, just like water is identical

to H2O.

Epiphenominalism

Qualia are causally

impotent.

Jackson

The “Landscape”

Descartes

•  I can conceive of myself without a body, – As a disembodied mind.

•  I cannot conceive of myself without a mind, – As a mindless zombie.

•  So, having/being a mind is an essential property, while

•  Having a body is merely an accidental property.

Life After Death?

•  If there is such a thing as life after death, then there must be a “part” of you that continues to exist after the death of your body.

•  So, if you believe in life after death, you are already committed to the idea that you are something distinct from your body … –  i.e., distinct from any material object.

Descartes

•  A Dualist – Descartes thinks that what I am is a mind, and that

I occupy a material body. •  “Thinking” (being conscious) is an essential property. •  “Being extended” (occupying space—having a body) is

merely an accidental property.

– So, there are two fundamental and distinct basic kinds of stuff: mind and matter.

Mind/Body (or Substance) Dualism: There are two distinct, fundamental and irreducible,

sorts of things in the world…

MINDS

•  Conscious Beings: –  Non-material beings which

are the subjects of conscious experience.

•  Descartes: –  Res cogitans –  “Thinking” but non-extended

beings (beings that do not occupy space).

BODIES (Matter)

•  Material Beings: –  Material (“corporeal”) beings

that cannot be the subjects of conscious experience.

•  Descartes: –  Res extensa –  Extended beings (beings that

occupy space), but are not capable of “thinking.”

Descartes’ Arguments for Dualism

•  Bodies are divisible. Minds are not. So they cannot be one and the same thing.

•  “Mind” and “Matter” are conceptually distinct—the concept of each is independent of the concept of the other. So it is conceptually possible for one to exist without the other. So they must be metaphysically distinct.

A Problem: Causal Interaction

•  On Descartes’ view (dualism), minds and bodies are fundamentally distinct kinds of things, distinct kinds of “substance.”

•  And yet, he believes they causally interact with one another. – Exp.: Sense perception, willful action.

•  But it seems impossible to explain how things with nothing in common could “influence” each other.

What are “Mental States?”

•  A “mental state” is just a state or condition some person might be in, like seeing, thinking, being in pain, willing, desiring, etc. –  So, thoughts, pains, desires, beliefs, etc., are all “mental

states.”

•  We will use this term in a “neutral” way, that is, without presupposing either dualism or materialism. –  We need to have some way of talking about these things that

doesn’t “takes sides” in the dispute.

The Options

•  According to the dualist, mental states are states of an immaterial mind or soul.

•  There are different varieties of materialism: – According to the Identity Theory (which

Carruthers supports) mental states are identical to brain states.

– According to Eliminative Materialism (a version of which was held my Graziano), there are no such things as mental states.

Two Varieties of Materialism:

The Identity Theory: •  Mental states (thoughts,

sensations, etc.), are identical to states of the brain and/or central nervous system:

–  In the way in which water is identical to H2O, or lightning is identical to discharges of electricity in the atmosphere.

Eliminative Materialism: •  There really are no such things

as “mental states” (“thoughts,” “sensations,” etc.):

–  Like ghosts or “caloric,” we used to believe in them. We haven’t learned what they “really” are (what they are “identical to”): rather, we have learned that they really aren’t, i.e., that there are no such things.

Carruthers: Identity Theory

•  Carruthers turns a problem for dualism into an argument against it (an argument for “the identity” theory). – 1) Only physical events can cause physical events; – 2) Yet thoughts (mental states) can cause physical

events (willful action); – 3) So thoughts (and other mental states) must be

(must be “identical to”) physical events.

The Identity Theory •  Rejects Dualism: a variety of Materialism. •  Claims that everything that exists is, ultimately,

material. •  Unlike Eliminative Materialism, accepts that

mental states are, in some sense, “real.” •  But claims that what they really are are states of

the brain and/or central nervous system. – So thoughts (and other “mental states”) are identical

to brain states in just the way that water is identical to H2O.

Carruthers and Leibniz’ Law

•  Carruthers argues that mental states are identical to brain states: dualists disagree.

•  So, the debate concerns whether or not these things are identical.

•  Leibniz’ Law states a general truth about identical things: if two things are identical, they have the same properties. – So if things have different properties, they

cannot be identical.

Carruthers’ Rebuttals

•  Objection: The Argument from Certainty –  I can be certain of mental states, but not brain

states. – C: “being such that I can be certain about it” is

not a property that things have. •  Objection: The Argument from Color –  I can have green after-images, but brain states

can’t be green. – C: After-images aren’t actually green.

How many kinds of “stuff?”

Dualism: Minds and

Matter

Descartes

Monism:

Idealism: Everything is mental

Berkeley

Materialism: Everything is

material

Eliminative Materialism

There are no mental states,

just like there are

no ghosts.

Graziano

Identity Theory

Mental states are

identical to brain

states, just like water is identical

to H2O.

Epiphenominalism

Qualia are causally

impotent.

Jackson

The “Landscape”

Jackson

•  A “Qualia Freak” – Qualia: What it’s like to smell a rose, etc.

•  There are “truths” about what it is like to smell a rose, etc.

•  These are not “truths” of physics. •  So, there are truths that are not truths of

physics.

Jackson’s Dilemma

•  Jackson recognizes there are truths about what it is like to smell a rose;

•  And believes that these truths are not truths of physics.

•  Dilemma: Doesn’t claiming there are truths that are not truths of physics force one into dualism? Doesn’t this force one to reject materialism?

Jackson’s Solution •  Distinguish (mere) “Materialism” from (what

he calls) “Physicalism.” – Materialism: Everything that exists is material. – Physicalism: Materialism plus the claim that all

truths are truths of physics. •  Jackson is forced to reject physicalism. •  But accepting materialism while rejecting

physicalism leaves him with Epiphenomenalism.

Epiphenomenalism •  What you get if you accept qualia (truths

about what experience is like) while rejecting dualism.

•  Qualia are real, but causally impotent: they are caused by physical events, but cannot themselves cause physical events.

•  So, the world wouldn’t be any different if we were all “zombies.” – Consciousness is “real” but doesn’t do anything.

Why can’t qualia cause?

•  According to science, all causes are physical, and so must be describable in the terms of physics.

•  But qualia, Jackson has argued, cannot be described in the terms of physics –  (Facts about them are not facts of physics.)

•  So, qualia cannot be the causes of physical events. •  Epiphenomenalism is the view that qualia real, but

causally impotent.

Mental States and Causality

The Turing Test

•  How could we tell whether or not a computer could “think?” How could we tell if it was “conscious?”

•  Turing proposes a “test,” and says if a computer could pass it, we would have to say that it thinks. – The test involves answering question in a way that

could “fool” us into believing we were talking to a human being.

The Issue

•  Turing’s discussion of the “Objection from Consciousness” helps us understand the core of the issue.

•  We cannot see “inside” other people’s minds, and yet we believe they are conscious. –  So, we must believe this because of how they “behave”—

specifically, how they “talk.” –  If a computer behaves in the same way, we must either

admit that it thinks or deny that other people think, because we use the same “test” in both cases.