When Descartes says, I have a clear understanding of myself as something that thinks and need not be extended,
all that we should allow him is that for all he knows, he is something that thinks and isn't extended from that.
It doesn't follow that he actually is something that thinks and isn't extended.
So Descartes arguments for dualism are not actually particularly strong ones.
If we draw this this clear distinction between epistemology and metaphysics, we refuse to draw inferences from what?
From the fact that we simply have doubts or do not know things.
Then it's hard to get to substance dualism.
There are also some major problems for Cartesian dualism. One of them a famous problem.
How can two such distinct substances interact at all? A problem that's very often thrown at Descartes.
If I consist of mind and body and the mind is purely mental, it thinks.
But it's not extended and the body is purely extended and doesn't think, how can the two ever come into contact with each other?
Seems very hard to understand. Now, this is a real problem for Descartes because Descartes thinks causation is ultimately intelligible.
He thinks we ought to be able to make sense of causation as, for example,
when he says that any calls must have as much perfection or reality as its effect.
He's claiming to have an insight into how things cause other things.
But if we take David Hume's view of causation, then the position is very different.
Remember, David Hume came in the wake of people like Newton and Berkeley, and Newton had said when it came to gravitation, sure, we can't understand.
We can't make intelligible why one object attracts another with a false inversely proportional to the square of the distance.
But when we look at the way things work in the world, it turns out this is what happens.
And Hume generalise that and said quite generally, even with billiard balls, actually,
when you think about one billiard ball bashing into another, it's very familiar.
So it has that feeling of naturalness about it because it's familiar.
But if you put yourself in the position of Adam, the first man who's never seen billiard balls before,
he would be as mystified by that as we are mystified by gravity. If you think causation just ultimately is a matter of one thing following another,
what we call law like connexion, then why shouldn't there be law like connexions between mind and body?
So there's a bit of a sort of nice irony here that that Hume,
who have all these four lost the philosophers of this period, is probably most opposed to Descartes.
Actually, if you take a human view of causation,
what looks like a really serious problem for Descartes actually goes away, doesn't actually go away completely.
There is a genuine issue here about how you would even try to formulate the sorts
of laws that might hold between a mental substance and a physical substance,
even if you don't go with them.
The problem of intelligibility, even if you don't demand that the causal laws be intrinsically intelligible or natural,
trying to formulate any sorts of laws that you might have to connect physical phenomena with mental phenomena is quite a challenge.
Another problem commonly thrown at dualism hinges on the causal closure principle of the causal closure of physics.
The idea of this is that only physical events can cause physical events.
So physics is causally closed in the sense that if you want to look for an explanation of any physical phenomenon,
you have to look at physical things.
Now, it's often said this is a major problem for Cartesian dualism, because if you're a dualist, then it looks like you have to deny causal closure.
Why? Well, because mental events are causing physical events all the time.
I choose to raise my arm. That's a mental choice. And yet it has a physical effect.
But if the behaviour of my arm is entirely determined by physical causes, what room is there for a distinct mental cause?
How can it be some other substance, some mental substance influencing the behaviour of this physical substance?
But in fact, I don't think the causal closure principle is nearly as worrying for for dualism,
as many think, because the question is what basis do we have for believing it?
Why should we believe that physics is closed in that way?
And we do these experiments in the laboratory, all sorts of very clever experiments that measure things to fantastic precision.
Sure, there we might find that everything is explicable in physical terms,
but nobody's ever tried to do any sort of realistic experiment on what's actually going on in a human brain when we think if it were,
in fact the case that there was an immaterial substance there influencing how the atoms move.
How on earth would you know? So it looks a bit like a prejudice, the same kind of prejudice that when Einstein famously said God doesn't play dice.
In other words, in Einstein's view, everything in the world is physically determined.
He was just voicing a prejudice. He didn't have a good reason for saying that.
Of course, the progress of science can lead us to think that everything will be explained in due course in terms of physical laws.
But the idea that we're anywhere near close to doing that is just fantasy.
So I don't actually think that objection is nearly as strong.
The causal closure principle seems really to to voice more and ambition or an aim of science rather than anything that we've discovered.
But even if we do deny the principle, certainly mind body interaction seems peculiar,
more significantly, I think it's hard to see how an immaterial mind could have evolved.
I think objections from the theory theory of evolution are far more worrisome for the duellist.
Do animals have minds? At what point in the sequence of evolution do minds appear?
Or do you have to say that minds are not all or nothing?
If you're going to allow a mind to evolve as a separate substance, does it mean you've got to have separate substance right there at the start?
Amoebae and so on. Microbe's. OK, so we move away from dualism, where are we left?
What can we have? Well, interaction ISM tells us, but mind and body interact in the pretty common sense way.
Mind can causally influence the body. Body can causally influence the mind epiphenomenal ism.
Some people are driven to that by trying to make sense of all this. They say that the mind is just an epiphenomenon.
It doesn't actually have any causal effect on the body. It's just a sort of irrelevant spin off.
The body works away. It does its stuff. The mind floats above it, as it were.
We feel these things. We think these things. But actually, everything is determined by the body.
Physicalism, the theory that all there is is physical stuff.
There's nothing to the mind beyond the physical brain. It's important to know these terms like epiphenomenal ism.
You find them bandied around a lot in the literature. Another view is property dualism, and this can be combined with some of those others.
And there's a famous argument for this known as the knowledge argument of Frank Jackson.
Imagine a scientist, let's call a Mary who learns all the physical facts about colour and colour perception,
but who for some reason cannot see colour. Certainly got rods in her eyes.
No cones or something like that. So no colour perception at all.
But rather peculiarly has it has devoted her life to investigating colour.
She knows all the facts there are about colour. Then wonderfully, she's given normal sight by whatever means some new operation.
And suddenly she can actually see colour as well. She learns what colours look like.
And it looks, doesn't it, as though she has learnt something new, something she did not know before.
She now knows how colours look. So it's tempting to say from this sort of argument.
But since she knew all the physical facts before she'd studied colour science, she knew all the physical stuff.
The new thing that she learns how colours look. That must be something non-physical.
So this can seem like an argument that forces you maybe not into substance dualism, not into saying that mind and body are distinct substances,
but at any rate, to saying that they're quite distinct properties, physical properties, mental properties.
But hang on a minute. What do we mean? You don't have the sheet, by the way.
You'll be getting these next six slot slides next time with the ones on knowledge.
What do we mean by physical stuff? What do we mean by physical properties?
This is actually a really big problem these days back in the 17th and 18th centuries.
Everybody knew what a physical cause was. You know, physical stuff is just extended inert stuff like billiard balls or stones.
It just bashes into each other, does whatever it does, brute physical matter.
But nowadays, our quantum scientists don't have brute physical matter like that.
They've got exotic stuff with all sorts of weird properties, charge, spin, charm, strangeness.
The further they deep they dig into the deep properties of the physical world, the weirder it becomes.
So what do we mean when we talk about a physical property? We don't mean assuredly what they meant in the 17th, the 19th centuries.
So let's suppose that our scientists came up with an explanation of consciousness that implied that even my new
parts of matter have some kind of proto consciousness from which our consciousness came through evolution.
Would that then make consciousness a physical property? Very weird.
Very strange to speculate like this.
But the point is to highlight that we don't actually have nearly as clear a concept of what a physical property is as we might wish.
Sure, physicalist don't like that kind of thing. It seems spooky and it won't matter.
Have these kind of ghost like consciousness. Sure. But maybe that's just the prejudice.
Maybe in 100 years time, the science that comes out will seem as weird to people now as quantum mechanics does now.
Two people a couple of hundred years ago. Now, without pursuing those sorts of spooky lines of enquiry.
It's also worth bearing in mind that we need to get much clearer on what we mean by
explanation and to be aware that you can have more than one kind of explanation.
Here's an example. Suppose I type in 11 times 12 equals on my calculator and it comes out with one hundred and thirty two.
Why? Why does it do that? Well, it's purely a physical object, right?
My calculator is not thinking. But if I want to explain why it does what it does, why it shows one hundred and thirty two.
Actually, the explanation is not a physical explanation.
You can give a physical explanation for why my calculator faithfully reproduces mathematical facts.
But the explanation as to why it comes up with that particular answer is a mathematical explanation, not a physical one.
Likewise, if you're playing a chess computer.
The reason why it moves its knight to Bishop three or whatever might be because that's the only move to guard against Checkmate.
The illuminating explanation of why it behaves as it does is not given in physical terms, even if it's a physical object.
Now, it's rather tempting to see the relation between brain and mind as analogous to that between hardware and software.
Think about that chess computer and think about the fact that our explanation of our
behaviour in mental terms is bound to be very different from a physical explanation.
That being so, just like the chess computer, there may be no need to hypothesise some spooky substance, some immaterial substance.
It might be simply that the way our bodies are put together is such that the best explanation of how we behave is to be given in intentional terms,
not in physical terms. As I say, in the case of the computer, there's nothing weird or strange about it.
Now, if the mind is something like the software of the body, something like a bodily process,
rather than a separate substance, that does make it distinct from the mind, but not a distinct stuff.
And this brings us to a very famous contribution of Gilbert Ryle.
He imagines a visitor to Oxford who says, I've seen all these colleges, all these offices.
Where's the university?
And that's because they're going wrong, because they think the university is something separate from all the colleges and offices.
It isn't. Now, maybe the same thing is going on when people talk about minds.
They see the body. They see the bodies behaviour and then say, yes, where's the mind?
Maybe the mind just is having a body that behaves in an appropriate way.
Many minds problem, I've put that slide in just because you will come across it in the reading that you do on this topic.
Another strange consequence of thinking of the mind as a separate substance from the body is that it
raises the apparently absurd worry that you might have more than one mind associated with the same body.
But I want to end by mentioning the hard problem as it is known now,
suppose you accept what I've been saying about how the arguments for a separate substance don't seem to be very good,
seem to be all sorts of problems with thinking of mind as a separate substance.
On the other hand, when we think of the behaviour of computers,
we can see that we have to draw a distinction between the physical object and the explanation of its behaviour.
We can see that the explanation of how an object behaves might need to be put in non-physical terms in order to be illuminating.
And the same clearly applies to us. We have evolved as purposive animals.
The way we behave is often best explained in terms of those purposes, not directly in physical terms.
But still, there's a problem, isn't there? Suppose I look at that light.
I'm aware of it. Something is going on there.
I feel that everything physical could be going on in my head just as it is now with all the same causal laws.
And yet it not to be accompanied by that awareness that I have of that light.
The phenomenal quality of it where I hit myself on the desk here and I feel a bit of pain.
Why can't the physical things go on exactly as they are without that feel?
And that, I think, remains the core of the problem of mind and body consciousness.
We feel that we are directly aware of something substantial there, maybe not in the sense of a separate substance,
but a real phenomenon that is not just a matter of physical behaviour.
And I think that feeling, whether justified or not, lies behind the continuing puzzlement that philosophers do feel about this problem.
I've sketched some of the approaches to that, some of the ways in which Cartesian dualism certainly doesn't seem to be an adequate solution to it.
But this is definitely a problem that is going to run and run for some time yet.
Thank you.