The Science of Discworld IV Judgement Da - By Terry Pratchett, Ian Stewart Page 0,27

1779 Dialogues Concerning Natural Religion. The context was a discussion of a creator God as an explanation of the material world. The obvious question ‘what created God?’ leads all too naturally to ‘creators all the way back’, a line of thinking that Hume wanted to close off. He says:

Have we not the same reason to trace that ideal world into another ideal world, or new intelligent principle? But if we stop, and go no further; why go so far? Why not stop at the material world? … after all, what satisfaction is there in that infinite progression? … If the material world rests upon a similar ideal world, this ideal world must rest upon some other; and so on, without end. It were better, therefore, never to look beyond the present material world. By supposing it to contain the principle of its order within itself, we really assert it to be God; and the sooner we arrive at that Divine Being, so much the better. When you go one step beyond the mundane system, you only excite an inquisitive humour which it is impossible ever to satisfy.

In short, if we identify God with the material universe, we need go no further, and that’s great because it stops us asking awkward questions. However, this does seem to imply that the universe created itself. And that seems to leave open exactly the line of thinking that Hume was trying to close (but Spinoza, two hundred years earlier, had already espoused that idea…).

Other scientific issues can be similarly swayed by human psychology. It is difficult to imagine Einstein’s curved space (though not impossible for a trained mathematician or physicist), because we foolishly ask ‘curved round what?’ The answer is that it’s not curved round anything – it’s just curved. Its natural metric – its mathematical measure of distance – is not flat. Space seems to bunch up or spread out compared to a naive model based on Euclid’s geometry. On the other hand, we are very happy with an infinite flat Euclidean plane or its three-dimensional analogue, space. It never occurs to us to ask ‘flat along what?’ But it’s an equally sensible (or equally senseless) question.

These cognitive biases probably stem from the model of space that our brains have evolved to contain, which seems to be Euclidean. This may perhaps be the simplest model that fits our experiences of the nearby world, extrapolated in the simplest way to avoid space having a boundary. Which would be appealing because we don’t see any boundary. Our minds are very parochial. Our model of causality presumably evolved to match sequences of events that are common in our immediate vicinity, the human-scale world.

When it comes to the crunch, looking at both the theory that time had a specific origin, a finite period into the past, and the theory that it did not, but has always been in existence, then both have inherent flaws. This suggests that we are not thinking about the right question. Our view of the universe may be just as parochial and unreasonable as the world-bearing animals of ancient cultures were. Future scientists may view both the Big Bang, and four elephants riding on a turtle, as conceptual errors of a very similar kind.

fn1 Like all really nice stories this tale, told by a ‘country parson’, may be false. Other versions say that Newton kept losing time from his research by letting the cat out. Selig Brodetsky’s Sir Isaac Newton and Louis Trenchard More’s Isaac Newton: a Biography both state that the great mathematician did not allow either a cat or a dog to enter his chamber. But in 1827 J.M.F. Wright, who lived in Newton’s former rooms at Trinity College, Cambridge, wrote that the door once had two holes – by then filled in – of the right size for a cat and a kitten.

fn2 Jay Miller, Why the world is on the back of a turtle, Man 9 (1974) 306–308.

fn3 It’s fascinating how priests always know the names of the gods.

fn4 A 10,000-mile long drift net built to catch items falling over the edge.

fn5 In 1857 Philip Gosse wrote a book called Omphalos: An Attempt to Untie the Geological Knot that argued for this approach – see The Science of Discworld II: The Globe.

fn6 In his 1967 Constraints on Variables in Syntax the linguist John R. Ross states that it was the psychologist/philosopher William James. In other sources the scientist is variously identified as Arthur Stanley Eddington, Thomas Huxley, Linus Pauling,