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So the attack on resemblance on the resemblance thesis naturally leads us to an attack based on our lack of understanding of the qualities concerned.

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So here you can see empiricism playing a big role.

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Remember, Locke is very notable for his empiricism, for insisting that all our ideas must derive from experience.

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All our ideas are copied, as it were, from experience. Berkeley and Hume both follow him in this.

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But if our ideas are copied from experience,

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then it seems that our ideas of primary qualities must be infused with the experiential qualities through which we experience them.

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When I see a shape, a circular shape, I see it as coloured.

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It's only because it's coloured that I can see it at all.

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Well, if that's so, what doesn't it follow that my idea of a shape must intrinsically be coloured?

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And if secondary qualities like colour cannot exist except in the mind, then the same is going to go for the primary qualities.

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Isn't it? Well, maybe not.

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Why can't I see a yellow circle?

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A blue circle. A red circle and so forth, and then form the abstract idea of a circle.

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Just a circle, not with any particular colour. Why can't I do that?

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In which case that idea of circularity is not going to be, as it were, contaminated with subjective secondary qualities.

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Maybe I can form the idea of something which is circular but not coloured.

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Well, Barkley and Hume both attack Locke, saying that we cannot do this and they attack Locke on the doctrine of abstraction.

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Now, you may remember, Locke, that doctrine of abstraction is that we form general ideas by leaving out detail.

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So, for example, a child, the first man that child gets to know is probably his father.

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So the child forms the idea of his father. Then he begins to meet other men and notices their similarity and notices their difference.

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No doubt from the women that he meets and then he forms the abstract idea of a man by leaving out details.

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So some many meet a tall, some are short, some in fact, some of them thin, some adopt some affair, some a beard, some don't.

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The child forms the abstract idea of a man by leaving out all the distinctive features and just retaining the general features of manliness.

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So that's loks doctrine of abstraction. Berkeley very strongly attacks it.

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He says you can't do that.

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There's no way you can form the idea of a man who is neither tall nor short nor fat nor thin, nor with a beard, nor without one.

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That's inconsistent. You cannot imagine such a thing because such a thing cannot exist in reality any more than

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you can form the idea of a triangle which is neither equilateral nor isosceles nor scaling.

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It's impossible to do these things. And when you read Berkeley, you might wonder why.

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Why is he making such a big thing about abstraction? Why is it so important to him?

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Well, the reason that it's important to him comes back to this business of primary and secondary qualities.

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Wants to say that I cannot form the idea of a circle which has no colour.

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And if I can't form the idea of a primary quality circle without the second derogatory quality colour,

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and if all my ideas of secondary qualities are intrinsically mental, they cannot exist outside the mind.

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Then it follows that I cannot even conceive of a primary quality which can exist independently of the mind.

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I cannot form that conception. And that's why he put such a lot of emphasis on it.

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If you read Barclays' Principles, most of the introduction is devoted to an attack on abstraction.

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That's why. So Barkley concludes from this argument that bodies independent of mind are literally inconceivable.

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You cannot even conceive of an object existing outside the mind.

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Now, if that's right, then it follows that the world has to consist ultimately of mental entities, spirits and ideas.

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So you get to Barkley's famous idealism. Now, most of us probably are not going to be very attracted by idealism,

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it seems the kind of extravagant metaphysical nonsense that philosophers love spouting but no commonsensical person could possibly believe.

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Samuel Johnson is famously said to have discussed Berkeley in these terms, kicking a stone.

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He said, I refute him thus. And the idea was that the solidity of the stone clearly shows that real physical objects exist outside minds.

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Well, suppose we want to have a rather more considered reaction to Berkeley.

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The right thing to do seems to be just to concede that our notion of body is not likely to be ultimately

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composed of elements that we can fully understand in these kinds of terms that Locke thought we could.

48
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If we try to form an idea of body as consisting entirely of properties that resemble our ideas,

49
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then we have this problem of understanding what it is that fills the space.

50
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And maybe we just have to concede. This in the case of a property like solidity.

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We just can't do that. We have to attribute body is having a something I know not what that fills the space.

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Is that a problem?

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Well, Barkley and Co wanted to say that was a problem, that a theory that attributes to something I know not what is no theory at all.

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But actually, we can see with the progress of modern science that this has become a much more familiar idea.

55
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Okay. At the time, the best physical theory, the corpuscular arean theory, had this interesting coincidence that the properties attributed to matter.

56
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Were at the same time properties that seemed intrinsically intelligible, that made sense.

57
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Again, Locke wanted to say that in praising the corpuscular in hypothesis,

58
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he praises the fact that it is so intelligible shape, size, motion, these are things that we can understand readily enough.

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And it seems to make sense when one thing bashes into another and makes it move.

60
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It's got that kind of intrinsic intelligibility. So we naturally get the idea that the fundamental problem properties of matter,

61
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the properties in terms of which we're explaining everything, including matters, appearance.

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Those properties are ones which are intelligible to us. Then we look critically at solidity and we find actually maybe it's not so simple.

63
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Maybe we in order to draw a distinction between matter and empty space.

64
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We have to attribute this crucial property solidity or something like that,

65
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which is a property that we can only understand indirectly in dispositional terms in terms of what it does.

66
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We have to say there's this something we know, not what that keeps other. Something we know not what's out.

67
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And that looks at first to be. Undesirable.

68
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But then you look at modern theories and you see things like mass charge spin.

69
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Strangeness. All these funny properties that we start attributing to fundamental particles.

70
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We come up with things like quantum mechanics,

71
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where we more or less have to give up any attempt to understand the fundamental properties of things in terms that we find naturally intelligible.

72
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And we have to face up to the fact that it has evolved creatures. Our senses are naturally fitted to understand the world at one level.

73
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But that doesn't mean by any means that our intuitive understanding is going to work all the way down.

74
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So maybe we just have to accept that our best theories are quite likely to attribute fundamental

75
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properties to objects which are radically different from anything that we are intuitively aware of.

76
00:09:07,570 --> 00:09:13,300
So we do have to say, well, is this something I know not what which has this these properties.

77
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I call it charge. It can be either positive or negative.

78
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It has the property that a positive attracts a negative and a positive repels a positive and so forth.

79
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All I can do is give you equations at best which describe how these things behave.

80
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But if you say, what is it, all I can say is, well, it's something I know, not what that has these properties.

81
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So at the time, that looked unacceptable,

82
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I think the reason it looked unacceptable because the scientists at the time had this illusion, a very attractive illusion,

83
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that the world was going to be comprehensible and the illusion was fostered by having a physical theory,

84
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which seemed to be so intuitively neat and nice.

85
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The crack there comes with solidity, if you really push it, that you come to a quite different conclusion about the way in which ideal,

86
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what an ideal science can be, it cannot attribute ultimate properties that we will necessarily find intelligible.