Presentation on theme: "Descartes Meditations II and VI"— Presentation transcript:
1Descartes Meditations II and VI The Mind-Body ProblemDescartes Meditations II and VI
2Descartes’ Argument for Dualism: Meditation II Can I now claim to have any of the features that I used to think belong to a body? When I think about them really carefully, I find that they are all open to doubt…Thinking? At last I have discovered it—thought! This is the one thing that can’t be separated from me. I am, I exist—that is certain. But for how long? For as long as I am thinking. But perhaps no longer than that; for it might be that if I stopped thinking I would stop existing; and ·I have to treat that possibility as though it were actual, because· my present policy is to reject everything that isn’t necessarily true. Strictly speaking, then, I am simply a thing that thinks—a mind, or soul, or intellect, or reason.I can’t conceive of myself apart from thinkingWhat is inconceivable is impossibleTherefore it is impossible for me to exist apart from thinking: I am essentially a thinking being
3Problems I can’t conceive of myself apart from thinking But others can conceive of me apart from thinking! I can’t conceive of being dead—but other people can conceive of my being dead.And compare: I can’t conceive of myself not being here now…What is inconceivable is impossibleThis is the assumption that conceivability is criterial for logical possibility. But can we come up with a non-question-begging account of conceivability?Therefore it is impossible for me to exist apart from thinkingWhen we dreamlessly sleep? Are we gappy?
4Descartes’ Argument for Dualism: Meditation VI [T]he fact that I can vividly and clearly think of one thing apart from another assures me that the two things are distinct from one another— ·that is, that they are two·—since they can be separated by God. Never mind how they could be separated; that does not affect the judgment that they are distinct. ·So my mind is a distinct thing from my body. Furthermore, my mind is me, for the following reason·. I know that I exist and that nothing else belongs to my nature or essence except that I am a thinking thing; from this it follows that my essence consists solely in my being a thinking thing, even though there may be a body that is very closely joined to me. I have a vivid and clear idea of myself as something that thinks and isn’t extended, and one of body as something that is extended and does not think. So it is certain that am really distinct from my body and can exist without it.If one can clearly-and-distinctly conceive one thing apart from another then they are not identical.I can clearly-and-distinctly conceive of myself apart from my body.Therefore, I am not identical with my bodySo I can* exist apart from my body.
5Some Mind-Body Problems The ontological question: what are mental states and what are physical states? Is one class a subclass of the other, so that all mental states are physical, or vice versa? Or are mental states and physical states entirely distinct?The causal question: do physical states influence mental states? Do mental states influence physical states? If so, how?The problem of the self: what is the self? How is it related to the brain and the body?The problem of consciousness: what is consciousness? How is it related to the brain and the body?
6The Ontological Question: What is there? Physicalism: thesis that everything is physical or supervenes on the physical.Supervenience: no two possible worlds can be identical in their physical properties but differ, somewhere, in their mental, social or biological properties: if physicalism is true at our world, then no other world can be physically identical to it without being identical to it in all respects.A dot-matrix picture has global properties — it is symmetrical, it is cluttered, and whatnot — and yet all there is to the picture is dots and non-dots at each point of the matrix. The global properties are nothing but patterns in the dots. They supervene: no two pictures could differ in their global properties without differing, somewhere, in whether there is or there isn't a dot. [David Lewis]
7SupervenienceWhat these hedges are like at the leaf-and-branch level determines what the topiary looks likeBut hedges that were different at the leaf-and-branch level could have the same topiary look
8Non-Dualist Theories of Mind Physicalism: mental states are identical to or supervene upon physical states, in particular, brain states.(“Analytical” or “Logical”) Behaviorism: talk about mental states should be analyzed as talk about behavior and behavioral dispositionsThe Identity Theory (Type-Physicalism): mental states are identical to (so nothing more than) brain statesFunctionalism: mental states are to be characterized in terms of their causal relations to sensory inputs, behavioral outputs and other mental states, that is, in terms of their functional role.
9Dualist Theories of Mind Predicate Dualism: psychological or mentalistic predicates are (a) essential for a full description of the world and (b) are not reducible to physicalistic predicates.Compare to functional terms, e.g. hurricane.: irreducibly different in type but token identity between each individual hurricane and a mass of atoms.Property Dualism: There are two essentially different kinds of properties in the worldSubstance (“Cartesian”) Dualism: mental substance is distinct from material substanceSubstance: the thing which possesses properties.For substance dualists not only the properties but the substance that has them is immaterial
10The Causal Question—for Dualists Problems for InteractionismHow can such different kinds of things interact?Seems incompatible with closure of physicsProblems for EpiphenomenalismCounterintuitive: mental events seem to cause physical eventsEpiphenomena are inexplicable in evolutionary termsProblems for ParallelismInvokes pre-established harmony or very busy interventionist god.
11Epiphenomenalism Motivation for Epiphenomenalism All physical events have sufficient causes that are themselves physical eventsBut some mental events—qualitative states, the what-it-is-like experience—seem to be irreducibly nonphysical: it seems implausible to identify them with brain events.Problem: intuitively some mental states cause behaviorE. g. pain causes people to winceMoreover, part of what we mean by “pain” seems to involve an association* of with characteristic behavior*We’ll leave “association” intentionally vague
12The Self: Bundle Theories and Substance Theories Substance: Something that has properties. Not a property or bundle of properties or “mode” or arrangementIs the self a substance or a bundle of psychological states?Property Dualism vs. Substance DualismSubstance (“Cartesian”) Dualism: the self is an immaterial substance.Property Dualism: the self is not an immaterial substance but eithera bundle of immaterial states/eventsa material thing (e.g. a living organism) that has mental states
13Consciousness: “The Hard Problem” for Physicalists Qualia: the introspectively accessible, phenomenal aspects of our mental livesThomas Nagel in “What It Is Like to Be a Bat” argues that some facts can only be captured ‘from a subjective perspective’ and uses his example of bats to illustrate the pointEven if we knew everything there is to know ‘from an objective perspective’ about a bat's sonar system we still would not know ‘what it is like’ to perceive a given object with a bat's sonar system.
14(Philosophical) Behaviorism MotivationWe want to hold that there are no irreducibly non-physical causes of physical eventsBut we also need to accommodate the fact that what we mean by terms designating mental states involves an association with characteristic behavior.ProblemsIntuitively, there’s more to some mental states: the problem of qualiaIntuitively, there can be less to mental states: it’s conceivable that one may be in a given state without even being disposed to characteristic behavior—or that one may be disposed to uncharacteristic behavior (e.g. Lewis’ madman)Dispositions aren’t causes so, while behaviorism associates mental states with behavior, mental states don’t cause behavior.
15The Identity Theory Motivation We want to hold that there are no irreducibly non-physical causes of physical eventsBut we also want to understand them as “inner states” that are causally responsible for behaviorProblemsQualia again: intuitively there is more to consciousness than brain statesSpecies chauvinism: if we identify a type of mental state, e.g. pain, with a type of brain state that is responsible for pain in humans, e.g. the firing of C-fibers, what do we do about non- humans who don’t have the same kind of brain states but who, we believe, can nevertheless have the same kind of mental states? We want multiple realizability
16Problem for the Identity Theory: Multiple Realizability Are mental states just identical to brain states?Problem: It’s logically possible that two guys are in the same type mental state but different type brain states, i.e. that M1 = M2.But if M1 = B1 and M1 = M2 it is not logically possible that B1 ≠ B2!M2M1I see a red blob.I see a red blob.
17Problem for the Identity Theory: Multiple Realizability Are mental states just identical to brain states?Problem: It’s logically possible that two guys are in the same type mental state but different type brain states.But if M1 = B1 and M1 = M2 it is not logically possible that B1 ≠ B2!M2M1I see a red blob.Woof!
18Problem for the Identity Theory: Multiple Realizability Are mental states just identical to brain states?Problem: It’s logically possible that two guys are in the same type mental state but different type brain states.But if M1 = B1 and M1 = M2 it is not logically possible that B1 ≠ B2!M2M1I see a red blob.I see a red blob
19FunctionalismWhat makes something a mental state of a particular type does not depend on its internal constitution, but rather on the way it functions, or the role it plays, in the system of which it is a part.Topic Neutrality: mental state concepts don’t specify their intrinsic character, whether physical or non-physical—that’s a matter for empirical investigation. (compare natural kind concepts!)So Functionalism is in principle compatible with both physicalism and dualism—though dualism is unmotivated.Multiple Realizability: A single mental kind (property, state, event) can be "realized" by many distinct physical kinds.The same type of mental state could, in principle, be “realized” by different physical (or non-physical) statesDisagreement about how “liberal” we should be in this regard (compare, e.g. Block on the Chinese nation, the hive mind, etc.)
20Functionalism to the Rescue Functionalism: what makes something a thought, desire, pain (or any other mental state) depends not on its internal constitution, but solely on its function—the role it plays, in the cognitive system of which it is a part.The identity of a mental state is determined by its causal relations to sensory stimulations, other mental states, and behavior.I see a red blob.same outputI see a red blob.same input
21Multiple Realizability We’re in the same computational state!We’re in the same computational state!Mental states are like computational states of computersThe same computational or mental state can be realized by different hardware or brainware!
22Funtionalism and Qualia We have multiple realizability but some worries…Disagreement about how “liberal” we should be in this regard (compare, e.g. Block on the Chinese nation, the hive mind, etc.)Still can’t capture “what it is like”The Reversed SpectrumThe Knowledge Argument (“What Mary Didn’t Know”)The Zombie Argument
23Block’s Chinese Nation Thought Experiment Suppose that the whole nation of China was reordered to simulate the workings of a single brain (that is, to act as a mind according to functionalism). Each Chinese person acts as (say) a neuron, and communicates by special two-way radio in the corresponding way to the other people. The current mental state of China Brain is displayed on satellites that may be seen from anywhere in China. China Brain would then be connected via radio to a body, one that provides the sensory inputs and behavioral outputs of China Brain.Thus China Brain possesses all the elements of a functional description of mind: sensory inputs, behavioral outputs, and internal mental states causally connected to other mental states. If the nation of China can be made to act in this way, then, according to functionalism, this system would have a mind.
24The Hive MindIndividual bees aren’t too bright—but the swarm “behaves intelligently”Is there a hive mind?
25Functionalism Still Has a Problem with Qualia Intuitively there’s more to some mental states than input and output.There’s what they’re like for the individual that has them!And what they’re like might be different for different peopleI see a red blob.I see a red blob.
26Intentional vs. Qualitative Content Both of our experiences represent USDBut they have different qualitative contentTheir experiences have the same intentional content since they both are representations of the University of San Diego.They have different qualitative content since what it’s like for one person isn’t the same as what it’s like for the other.
27IntentionalityIntentionality is the power of minds to be about, to represent, or to stand for, things, properties and states of affairs.Reference is intentional in this sense: I think (and talk) about thingsPerceptions, beliefs, desires and intentions and many other “propositional attitudes” are mental states with intentionality: they have “content”Intentionality is directedness—understood by Brentano as the criterion for the mentalOnly mental states have intrinsic intentionality: other things have it only in a derivative sense to the extent that they are “directed” by intelligent beings.
28Intentional vs. Qualitative Content Intentional content: the way the experience represents the world, e.g. my experience represents the peppers as looking red.But my twin’s experience also represents the peppers as looking red: our experiences have the same intentional content.Qualitative content: what the experience “is like”: if these pictures represent my experience and my inverted-spectrum twin’s, our experiences differ with respect to qualitative content.
29The Inverted Spectrum Argument [T]he inverted spectrum argument is this: when you and I have experiences that have the intentional content looking red, your qualitative content is the same as the qualitative content that I have when my experience has the intentional content of looking green.Intentional content comes from functional role, i.e. aptness to be produced by certain inputs and to produce certain outputs.If an inverted spectrum is possible, then experiential contents that can be expressed in public language…are not qualitative contents but rather intentional contents.
30Knowledge Argument: Mary in the black & white room Mary is a brilliant scientist who is…forced to investigate the world from a black and white room via a black and white television monitor. She specializes in the neurophysiology of vision and acquires…all the physical information there is to obtain about what goes on when we see ripe tomatoes…and use terms like ‘red’…
31Mary gets out![W]hen Mary is released from her black and white room…It seems just obvious that she will learn something about the world and our visual experience of it.But then is it inescapable that her previous knowledge was incomplete.But she had all the physical information.Ergo there is more to have than that, and Physicalism is false.
33The Zombie ArgumentA (philosophical) zombie is a being which is a perfect duplicate of a normal human being—including brain and neural activity—but which is not conscious.The Zombie Argument for property dualismZombies are conceivableWhatever is conceivable is logically possibleTherefore (some) mental states/properties/events are not identical to any brain states/properties/eventsNote: this argument doesn’t purport to establish substance dualism or, as Descartes wished to show, that minds/persons could exist in a disembodied state!
34Dualism: Pro and Con Pro Qualia Irreducibility of psychology The Zombie ArgumentThe Cartesian Essentialist ArgumentConCausal closure of the physicalSimplicity
35Back to DescartesVivid and distinct conceivability as a test for logical possibilityDistinguish conceiving from imagining: I can conceive of a chilliagon even though I can’t imagine it.I can be mistaken about what I conceive of—so clearness and distinctness required.Something is possible if and only if I can conceive of itI can conceive of myself not having a bodyI can’t conceive of myself not existing (so long as I’m thinking, doubting or in any other mental state)So, it is possible for me to exit without having a body
36Descartes: I and my ideas exist for sure I will set aside anything that admits of the slightest doubt, treating it as though I had found it to be outright false; and I will carry on like that until I find something certain, or—at worst—until I become certain that there is no certainty.Cogito: Descartes proves his own existence!I undoubtedly exist: let him deceive me all he can, he will never bring it about that I am nothing while I think I am something. So after thoroughly thinking the matter through I conclude that this proposition, I am, I exist, must be true whenever I assert it or think it.Privileged Access: we can be certain about the existence and character of our own ideasBut not of the existence or character of the external things they purport to represent.
37Descartes Essentialist Argument for Dualism If I have a vivid and clear thought of something, God could have created it in a way that exactly corresponds to my thought [i.e. it’s logically possible]The fact that I can vividly and clearly think of one thing apart from another assures me that the two things are distinct from one another.By necessity of identity: if body and mind are possibly distinct then they’re actually distinct.So my mind is a distinct thing from my body.because I can conceive of my mind apart from my bodyFurthermore, my mind is me…my essence consists solely in my being a thinking thingbecause I can’t conceive of myself apart from my thinking, thinking.I am really distinct from my body and can exist without it.
38Problem with Cartesian Dualism “We do not need that hypothesis”: complex behavior can be explained without recourse to irreducibly non-physical states.Purely physical mechanisms can exhibit the kind of complex, flexible behavior, including learning characteristic of humans.All physical events have sufficient causes that are themselves physical eventsPhysicalism is an aggressor hypothesis: we explain more and more without recourse to non-physical events/statesAgency explanations are eliminated in favor of mechanistic explanations—including explanations for agency itself.Claims to the effect that non-physical events cause physical events introduces an even bigger mystery: what is the mechanism?
39Do we have a theory that can do all this? Make sense of consciousness: “The Hard Problem”Avoid commitment to irreducibly non-physical states, events or substancesExplain the causal role of mental states asEffects of physical eventsCauses of behaviorCauses of other mental eventsAllow for multiple realizability in order to avoid species chauvinismWe want to be able to ascribe the same kinds of mental states we have to humans who may be wired differently, other animals and, possibly to beings that don’t have brains at all, e.g. Martians, computers