Scientific method

Many of those who objected to Darwin believed that his ideas were unscientific. Two methods of inference were allowed: induction, generalizing from authenticated facts, and deduction, from axioms to testable conclusions. No animal or plant had ever been seen to change into another species, and so Darwin’s conclusions could not be inductive; and they also lacked the logical rigor of Euclidean geometry or mathematical physics. His theory was historical, and statistical: the statistics being informal, based on the idea that in general the individual with some small advantage is more likely to survive and propagate its kind. The great poet is one who expands the sphere of poetry; maybe Darwin’s greatness was to expand scientific method into new territory.

Huxley was among those who believed that scientific method could be taught even to those learning little science. Sophisticated induction was described, with examples, by Herschel in his Preliminary Discourse of 1831, written to introduce the physical sciences for a series of little books, ‘Lardner’s Cabinet Cyclopedia’ by Long-man in London, in the printing and publishing revolution associated with the ‘march of mind’. They were cheap, hardbound books: the average price of a book in England fell by 48 per cent in the

25 years after 1827 as they ceased to be items of luxury. Herschel’s book was greatly admired by JOHN STUART MILL, whose System of Logic, 1843, was a classic statement of inductive philosophy. Early in the century, men of science in Britain had claimed to be followers of Baconian induction, but their practice was not actually in accordance with it. William Whewell in Cambridge, closely connected with those there creating a school of mathematical physics, and aware of German post-Kantian philosophy, proposed in his Philosophy of the Inductive Sciences, 1840, the idea that one must intuitively get the right end of the stick before one can begin to collect facts. His version of scientific method was thus much closer to the hypothetico-deductive model. Darwin was by temperament a deductive reasoner, collecting facts to test an idea; the

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Origin is a splendid example of Whewell’s method, and Darwin was disappointed that Whewell greatly disapproved of the book.

Handling probability was one of the great triumphs of nineteenth-century science, beginning with Carl Gauss’s demonstration that astronomical observations cluster round the true result in a bell-shaped ‘error curve’, and Laplace’s mathematical analysis of probability. In Belgium, Lambert Quetelet was appointed to work at the observatory, but soon perceived that human characteristics also fell on a bell curve, and that in the mass human behaviour was highly predictable. He chilled the spines of readers of his Essay on Man (1835, English translation 1842) with murder rates, at just the same time that even backward Britain was collecting what were called vital statistics. These established how unhealthy great cities were compared to the countryside, and became an essential tool of government. In 1859, shortly before the Origin was published, James Clerk Maxwell announced his dynamical theory of gases, that they were composed of elastic particles moving on average faster as the gas warmed up. Thus in physics, too, statistics rather than straightforward causality seemed to underlie reality; and with Ernst Mach in the last years of the century, established Newtonian ideas of space and time also came under criticism.

Scientific method