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Okay. Today, the topic is a double one dealing with perception and the primary secondary quality distinction.

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These are very closely related topics, as we'll see the various luminaries here, all of whom have something to do with Oxford.

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Robert Boyle, who did his famous experiments more or less founding the science of chemistry in Oxford.

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John Locke of Christchurch. Bishop Berkeley, who died and is buried in Oxford.

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He was visiting his son, Christchurch at the time, A.J. Eyre,

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who was Wiccan professor of logic at New College, J.L. Austin, and Peter Straughan, whom we've already met.

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Now, as he explained in the introductory lectures.

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A lot of these problems arose precisely because of the development of modern science in the early modern period,

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in particular the move away from Aristotelian ism to a mechanical account of the world implied explaining perception,

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not in terms of some kind of thing coming from the object to the eye,

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which was somehow intrinsically similar to the object, so that we directly grasp its qualities,

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but rather in terms of causal intermediaries, particles or waves,

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little particles of light that bounce off the objects and come to our eyes

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and then interpreted by our brains in order to give us perception of objects.

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Now, obviously, the issue doesn't only affect organs of sight, but all of our senses.

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But most of the discussions of this period tend to be focussed on site or to some extent, touch.

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Those are the senses that seem to come closest to giving us a.

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A presentation of objects as they are altogether.

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Now, this kind of view of the world started, as we saw with Galileo and Descartes, but Locke's account is the one that was most influential.

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So when people discuss these issues,

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it's typically against the background of a Lockean account of perception and the primary secondary quality distinction.

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So what are objects like when we perceive objects?

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When we see them in particular? There are impressions caused in us, in our brain somehow by a means of our sense organs, particularly our eyes.

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But we hypothesise that these are caused by particles or waves of light coming from the objects and the properties of those particles or waves.

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Bear no resemblance at all to the objects themselves.

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They somehow convey that information.

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But we are aware that there is very complex processing goes that goes on with the particles or waves hitting the retina.

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Messages travelling down the optic nerve, somehow being synthesised by the brain and so on.

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First of all, it does imply that that intermediary process involves things that are quite unlike either the

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perceptions that we have mentally and also probably quite unlike the objects themselves.

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If we're thinking in terms of a mechanical paradigm that the best explanation of how things happen is basically things bashing into each other,

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then that naturally suggests that the explanation of all this process had better be in mechanical terms.

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We'll naturally see geometrical and dynamical properties,

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things like shape and size and motion as being the crucial causal determinants of what happens.

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Now, John Locke, as we've seen before, took over Boyle's corpuscular arean hypothesis.

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He mentions it actually explicitly in the essay only once, the book for part three, search a Section 16.

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He doesn't commit himself to this. He doesn't say this is definitely the right account of things.

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But he says this seems to come closest to an intelligible explanation of how things work.

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So the corpuscular arean hypotheses, a hypothesis explains the properties of different substances,

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say gold or lead or whatever it may be, as arising from their particular micro structure.

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So the hypothesis is that the micro structure of gold is different from the micro structure of lead in a way that explains their different properties,

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why they have the colour they do, why they melt at the temperature that they melt.

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Why they're as hard as they are and so on. So the micro structure is supposed to consist of lots of little corpuscles.

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Now these corpuscles are likely to vary between the different substances.

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Presumably they do vary. They might vary in shape, in size and in organisation.

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They might be differently packed, say.

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But the corpuscular arean hypothesis involves the conjecture that all of these corpuscles are made of the same stuff.

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So they may vary in their properties, shape and size and so on, but they're made of the same stuff, which Boyle called universal matter.

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And when Locke talks about pure substance in general, it seems likely that he is referring to the same kind of thing.

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Except, of course, when Locke talks about pure substance in general and the ideas we have of it,

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he doesn't want to commit himself to the corpuscular Aryan hypothesis. So he's talking about the stuff of which things are made.

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Whatever that is, on the corpuscular in hypothesis, it would be the universal matter from which the corpuscles are composed.

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So this underlying substance is hypothesised to have primary qualities, that is shape, size,

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movement, texture and what Boyle called impenetrability and what Locke called solidity.

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And these are the qualities which are supposed to belong, as it were, intrinsically to the stuff.

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And those are the qualities in terms of which the appearance of the stuff to us is to be explained.

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So the secondary qualities, things like colour, smell, taste,

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the qualities that appear to us are explained by the primary qualities they are in themselves.

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Nothing like what we see. So when I see something.

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Suppose I look at the light and I see it as yellow. There is nothing in the light remotely like my idea of yellowness.

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It's rather that the primary qualities somehow cause that idea in me.

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So being yellow is a matter of having the power to produce the idea of yellow.

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That phenomenal idea that we are familiar with from seeing yellow, it's having the power to produce that in an observer who's suitably placed.

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So let's focus on the problem here by considering the case of a circular hot plate.

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Suppose there's an electric hot plate on an oven and it's been heated up until it's glowing red hot.

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Okay, quite familiar. I bring my hand close to the hot plate and I feel warmth.

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I bring it still closer and I feel pain. Well, the sensations are felt, warmth and pain are clearly in the mind.

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We do not attribute the pain to the hotplate itself. We're not even tempted to do that.

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Warmth. Maybe less clear, but at least the felt sensation of warmth.

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We won't attribute that to it. The circular shape.

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Well, we are inclined to attribute that to the object, the hotplate really is circular.

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We think. What about the red colour? The red circle that we see when we look at the hot plate, is that in the mind or is it in the object?

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And you can see that there's a bit of a tension here.

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When we look at objects and see them as coloured, we're naturally inclined to think of the colour as they're in the object.

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But if we start speculating about the mechanisms of perception, as one naturally does it in the early modern period.

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And now, of course.

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You're naturally led to think, hang on, it can't be like that, though, we're inclined to attribute the redness to the thing itself.

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Actually, there's no way there can be anything remotely like the redness in the object.

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Now, there's a well-known text in Locke's essay, a book to Chapter eight, Section 10.

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Which is quite notorious. Lock here is drawing a distinction between primary and secondary qualities.

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And he is discussing what he understands by a secondary quality.

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So he talks about such qualities, which in truth are nothing in the objects themselves,

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but powers to produce various sensations in us by their primary qualities,

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i.e. by the bulk figure, texture and motion of their insensible parts as colours, sounds, tastes, etc.

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These I call secondary qualities. Okay. So you've got the primary qualities in the object, the bulk figure, texture, motion.

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You've got the secondary qualities, colours, sounds, tastes and so forth, which are,

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he says, nothing in the objects themselves but powers to produce ideas in us.

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Now, that comma before, but is rather unfortunate.

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It gives the impression that Locke is saying that secondary qualities are nothing in the objects themselves.

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That's quite different from saying that they're nothing in the object but powers, then nothing but powers.

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They are in the object, but they are powers. Now, some people have interpreted like one way, some the other.

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I think it's quite clear that Locke does think that secondary qualities are in object, but secondary qualities in objects are powers.

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Now, Berkeley read Locke as denying that secondary qualities are in objects.

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He thought Locke was saying that secondary qualities are just in the mind, not in objects.

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But Locke is actually pretty clear on the matter. If you look at his chapter on the adequacy of ideas, so I've quoted a little passage there.

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Now, an adequate idea is one which faithfully represents what it is the idea of.

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So whether an idea is adequate or not depends on the faithfulness of the representation

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and lock being a An empiricist is trying to find a suitable foundation for our knowledge.

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How can we know that any of our perceptions of the world are securely anchored in the way things are?

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And lot comes up with a very ingenious solution to this. It's really quite clever.

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Take the simple idea of yellow that I get from looking at something yellow, just that particular colour, not the shape, just the yellowness.

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And I ask myself, is that thing really yellow?

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Is my idea of yellow a faithful representation of what is there?

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And Locke says, yes, it is definitely simple ideas are certainly adequate because being intended to

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express nothing but the power in things to produce in the mind such a sensation,

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it follows. Since I see the yellow, the thing itself must have the power to produce that idea.

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And that's all I mean by calling it yellow, that it has that power. Therefore, my idea must be adequate.

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Very ingenious. If something causes the idea of yellow in me, then that is its being yellow.

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There's nothing more to being yellow than having the power to produce the idea in me.

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So at least we can tick off the simple ideas like yellow as corresponding to the way things are.

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Now that's quite important. It's an important epistemological point and a very subtle and clever one.

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Locke is saying that an object being yellow is not a matter of there being anything in the object that resembles my idea of yellow.

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It's simply a matter of the object having whatever qualities it is that normally a naturally produce the idea of yellow.

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So that gives us something solid epistemologically to build on. And this is just one example of a quite fundamental shift between Descartes and Locke.

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Descartes looks at a piece of wax in meditation, too,

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and finds that his sensory perceptions are leading him radically astray and reckons that the only way that he can get a proper,

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adequate idea of what's there is to use his intellect to penetrate into the nature of matter and see that its essence is extension.

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So Descartes wants to found everything on intellectual perception.

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But here is Locke founding everything on sensory perception and saying here we have a solid anchor.

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So it's quite a deep move. But at this point, I'm just mainly using it to to prove that Locke does think that secondary qualities are in objects.

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So when you read Locke and Berkeley on these things, it's worth bearing in mind that Berkeley and indeed Hume get Locke wrong in this particular.