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316 pages, Paperback
First published January 1, 1961
Since Galileo and Newton, dynamics has been made a branch of mathematics, and we no longer stop to question whether this can be legitimately done. In the complex equations of mathematical dynamics we assume that the way a body moves depends on how heavy it is, rather than (say) on its colour or its chemical make-up. Furthermore, dynamics - the science which explains why bodies change their position and motion as they do - is for us quite independent of other theories of change. Suppose some object we are studying alters its position, its shape, its material make-up, its colour, or its vital activites. We assume that each of these alterations is of a distinct kind, and we look to specialists in different sciences to explain them. We no longer see any but the most far-fetched analogies between (for example) a motor-car accelerating, a man growing old, a pool of water evaporating, and a dye fading. Dynamics, physiology, physical chemistry, and the rest, all have their own distinct subject-matters, explaining the processes which are their concern in terms of quite different sets of principles. P. 19
Should we criticise the Greek philosophers for this? Was it a failure on their part, not to have adopted earlier the practice of severe criticism in the light of controlled observation which is the heart of modern science's "experimental method"? In case one is tempted to be scornful, two things should be said. First, you can start asking which of two automobiles performs better - which has the better acceleration or petrol consumption - only when the rival cars are assembled and in working order; the Greek philosophers, rather, should be compared to those men who first envisaged the possibility of motor-cars, and who worked out for us the original tentative designs.Their theories were still only on the "drawing board".
Secondly, among the Greeks science was a purely intellectual enterprise. One which was not undertaken with any technological end in view, and which in this direction yielded only the slightest fruit. (...) The Babylonian astronomers had their noses kept forcibly to the ground by the practical demand for accurate prophecies and predictions. By contrast, the very fertility and freedom with which the Greeks speculated is connected with the fact that so little hung upon the soundness of its results. Suppose they had to pay for wild generalization, or unsound theorizing (...) then they might well have proceeded more cautiously. And if their originality and imagination had been shackled in this way, it would have been very much to our loss. p. 68
We really need not be surprised that the Greeks remained skeptical about Aristarcho's [helicocentrism]: rather, we should congraulate them on their good sense. In judging them as scientists - as rational interpreters of Nature, that is - the important thing surely is not to ask how many conclusions they reached which we still accept, but rather how far their conclusions were supported by the evidence then available. In so far as they allowed their judgement to be influenced by the weight of the evidence, they can be said to have thought scientifically. In the light of subsequent developments, we can dispose of their arguments for the geocentric theory. But, as matters stood then, they had equal scientific justification for rejecting Aristarcho's helicentric speculations. p. 138
It would be hard to exaggerate this change in the efficiency of scientific communication. Whereas the pace of scientific advance had depended earlier largely on the concentration of scholars in one and the same place, from now on men living at a distance from one anotherc could collaborate effectively. Before 1500, one can hardly speak of mathematical or scientific advances ever becoming "common knowledge": important insights were achieved at one place and time, only to be lost again in the next century, and scholars working in different cities took as their starting points quite different bodies of knowledge. From about 1550 one can fairly assume that anyone writing about, say, planetary dynamics has read most of hte existing material directly relevant to his work. Only in the twentieth century, when the stream of scientific publications has turned into a flood, does this cease to be a reasonable assumpotion; the age of original papers and books is being rapidly replaced by the age of "abstracts." p.202