S EL2211: Contexts

SEL2211: Contexts Lecture 8: The Mind/Body Problem

The last few lectures: • The Computational Theory of Mind • The mind uses algorithms to build up structured objects • Looked at various specific ways this is implemented Today: we pull the focus back to one of the ‘big’ questions in philosophy of mind • Set out the ‘mind/body problem’ in its historical form • Look at various reactions

The Philosophy of Mind • The sub-branch of philosophy that studies the mind and mental events & properties • What is consciousness? • How do you know things? • What does it mean to feel pain, perceive the color red, etc. • The broadest and most central question: the mind/body problem – what is ‘the mental’ and how does it relate to ‘the physical’?

Some history/background • “I think, therefore I am” • Invented the Cartesian coordinate system and analytic geometry • First major (Western) thinker to frame the mind/body relation as a problem to be solved (http://en.wikipedia.org/wiki/René_Descartes) René Descartes (1596-1650)

In Descartes’ time • No real distinction between ‘philosophy’ and ‘science’ • Just foundational questions on which some larger inquiry rested • Nobody now really reads Descartes’ ‘scientific’ work on vision, planetary motion, etc.; just the foundational stuff

Descartes’ theory of the world • The ‘mechanical philosophy’/contact mechanics • The world is made up of little atoms which interact when they strike one another (from http://www.physics.upenn.edu/uglabs/experiments/2D_collisions/)

Descartes’ capstone work: Meditations on First Philosophy • Explained all of animal world and most of human behavior (from http://www.xtimeline.com/evt/view.aspx?id=24505)

But there’s a problem • Human beings’ freedom of action • The language version of this: the ‘creative’ aspect of language use (Chomsky) • This can’t be explained by the mechanical philosophy (i.e., the stuff we know makes up the physical world) • The natural (and most of the animal) world is just like big clocks. If you specify the external conditions and specify how the machine is set up, you know for sure what it will do

Descartes’ (radical) conclusion • It’s not the stuff of the physical world that’s doing it. It’s a different kind of substance, called mind. • A perfectly logical, sensible, scientific move to make • I’ve got a good theory of the world which really works • It says the world has properties X, Y or Z • This phenomenon doesn’t have properties X, Y, Z • Therefore, it’s caused by something else

Relating the mental to the physical • Descartes reply: uh, yeah, there’s like these ‘animal spirit’ things…and, uh, they sort of connect up to the brain via the pineal gland….Yeah, that’s the ticket. • Some of Descartes’ followers just give up: “God did it.” • Modern science doesn’t believe in substance dualism anyway. There’s only one kind of stuff in the universe (materialism, physicalism).

But that doesn’t make the problem go away • Even if there’s no ‘thinking substance’, there are still mental properties (beliefs, thoughts, qualia). How do these cause physical things to happen? • How does actually this work on the physicalist/materialist conception?

Reductive Materialism • Mental events and phenomena reduce to brain states (chemical or neurological patterns) • Another way of saying this: they superveneon brain states • When you or I have a pain in our arm, or are perceiving the color red, we’re in the same brain state. That’s why it’s ‘the same thing’. • So only exact similarity of brain states guarantees exact similarity of mental events and phenomena

But there are problems • Can identity of brain state = identity of experience be maintained? • People’s brains are wired (sometimes radically) differently (even hemisphere-ectomies)

What is the actual brain-state? • Our current understanding of (some kinds of) pain: c-fibres firing • But c-fibres are based on carbon, so only carbon-based life-forms can have brain states based on c-fibres firing • Therefore, non-carbon-based life forms can’t feel pain in principle. • A Variant: Eliminative Materialism • Beliefs, fears, perceiving the color red are all like ‘demonic possession’ or ‘bodily humours’. The correct, final theory of human beings won’t refer to these concepts at all. They never existed.

An Alternative: Functionalism • A particular mental state just isits relation to other mental states and to various sensory inputs and behavioral outputs. • The state of feeling pain just is the constellation of a disposition to say ‘ouch’, being distracted, wondering whether you’ve hurt yourself, etc. etc. • Mental states are functions of the entire organism.

Turing machines are often explicitly invoked • If you freeze a Turing machine, it’s in a particular state Beliefs, qualia, etc. are similarly just snapshots of the state of an organism

Mental states are like mousetraps • Doesn’t matter how they work • Spring-loaded bar that pins it to a piece of wood • A net that falls from the ceiling • Mind-control paralysis ray • If it catches mice, it’s a mousetrap • So no problem about silicon-based life forms, etc. • As long as they have a disposition to say ‘ouch’, are distracted, wonder whether they’ve hurt themselves, etc. etc., they’re ‘feeling pain’ identically to us.

However, there are problems here too • Dispositions to behave often aren’t identical, but if you want to allow something looser than strict identity, it’s not clear how you’d actually do that without the whole thing collapsing • Block & Fodor 1972 – the damn/darn problem • Imagine two people who each hit their thumb with a hammer. One says damn! and the other says darn! • Intuitively, you want to say these people are in the same mental state (feeling a specific pain), but they can’t be, since their behavior is different.

Block & Fodor 1972 – the damn/darn problem • You might say “well saying damn and darn ARE the same behavior (they’re both expressions of surprise and pain)”, but that’s circular. • You might say “well, the fact that they happened to exclaim something isn’t a relevant behavior”, but then you need an independent way of determining what’s ‘relevant’ behavior and what isn’t. That looks very, very, very hard.

Chomsky on the mind/body problem • The whole thing’s a misguided waste of time. There is no issue. • Basically: you can only have a mind/body problem to the extent that you know what body means. If you don’t know what you’re talking about when you talk about body (i.e. the stuff that makes up the physical world), it makes no sense to say certain things fall outside its limits.

Isaac Newton, destroyer of body • Descartes had a notion of ‘body’ – mechanical philosophy • Newton tries to extend this to planetary motion, but ends up destroying the concept. • Things can interact without there being direct contact (i.e., gravity)

Hence Newton’s big work is called Principles of Mathematics – a retreat to instrumentalism But now we’d say Newton was wrong. Gravity really does exist.

So what does this have to do with Chomsky? • His point is this: Descartes had a definite, fixed conception of body, but we today don’t. • Does space really have 11 dimensions? Or is it 13? • ‘Body’ just keeps evolving in order to accommodate whatever discoveries we make (cf. dark matter) (from http://www.physorg.com/news176125202.html)

Since we know we don’t have the ‘right’ or ‘ultimate’ view of what the physical universe actually is, you can’t say for definite that something (like thoughts) in principle falls outside its limits.

We can’t yet explain (in terms of quantum mechanics) how water flows down a drain, but philosophers don’t think that raises a ‘plumbing/body’ problem

You just divide the world up into research areas that seem to make sense, where you have facts that seem to fall together, and you try to gain some under-standing. So it looks like there’s phenomena in the world that look electrical, and chemical, and mental.

S EL2211: Contexts