Carving at the Joints

A.W. Moore

  • Writing the Book of the World by Theodore Sider
    Oxford, 318 pp, £30.00, November 2011, ISBN 978 0 19 969790 8

The world, according to Ted Sider, has a basic structure. An optimal description of the world must capture this structure. It must also consist of truths. But these are two distinct requirements. We can produce more and more truths about the world and still not come any closer to capturing its structure. To do the latter we need to produce not just truths, but truths of the right sort. Now it has long been acknowledged that a mere assemblage of truths does not count for much. They might be uninteresting and insignificant truths; for that matter, they might be interesting and significant truths, but assembled in an uninteresting and insignificant way – without any attempt at systematisation or explanation, without any attempt to establish connections. The idea of basic structure gives a further fillip to this familiar fact. It signals another respect in which, if we are to give the best possible account of the world, we need to do more than tell the truth. The concepts we use to couch the truth – the properties to which we advert, the sorts of thing we recognise as instantiating these properties, even the connectives we use to conjoin claims about such things – need to reflect the world’s basic structure. They need to ‘carve at the joints’. There is a privileged way to write the book of the world.

In the course of defending this vision, Sider works through an impressive list of philosophical problems and shows in each case how the idea of basic structure can help us address them. I shall give just two examples. First, consider the fact that some questions seem intuitively insubstantial. For instance: Is Snowdon high enough to be a mountain? Even if this question has a correct answer, it still seems insubstantial. We feel that nothing of importance separates us from a community whose understanding of what counts as a mountain is sufficiently different from ours that they would answer their analogous question differently. By contrast, the question of whether Snowdon is high enough to prevent the planet Venus from being seen from a given location at a given time does seem substantial. It is surprisingly difficult, however, to articulate what the distinction consists in. Sider is able to give an account of it. On his view, a question is insubstantial if one of the expressions used to formulate the question (‘mountain’ in this case) has a range of equally good available meanings, on some of which the question is to be answered one way and on some of which the question is to be answered the opposite way, where what makes two or more meanings equally good is the fact that none of them does better than the others in carving at the joints. The difference between mountains and mere hills is not part of the basic structure of the world, it is just a matter of how we happen to carve things up.

The second example concerns the philosophy of time. Participants in debates about the fundamental nature of time use various metaphors to illustrate their different conceptions. Thus we hear talk of a four-dimensional ‘block universe’. Sometimes this is supplemented with talk of a ‘moving spotlight’ that illuminates different parts of the block at different times. Sometimes the block is allowed to ‘grow’ over time. Then there is talk of the ‘flow’ of time. Other examples abound. But vivid though these metaphors are, it is irresistible, after a while, to wonder whether they represent genuine differences of view. There are two concerns. The less serious concern is that there is nothing genuinely separating the views to which these metaphors give expression. The more serious concern is that these metaphors do not give expression to genuine views in the first place. Sider is able to arrest such scepticism. He argues that there are indeed genuine views involved, and that there are genuine differences between them. Participants in these debates can be represented as differing about the basic structure of the world. Suppose that the expression ‘there are’ can be understood in such a way that it carves well at the joints. In these terms, some of the participants in the debates about time – those who are liable to express their view by saying that the past is as real as the present – can be represented as believing that there are, say, dinosaurs. Others – those who are liable to express their view by saying that nothing is true unless it is true now – can be represented as believing that there are no such things.

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