THE UNITY OF SCIENCE. 37 



tions. It cannot be normal that a man should cher- 

 ish incompatible ideas. But that is not to say that 

 he may not be both scientific and metaphysical, or 

 both scientific and poetical. These are indeed 

 different moods, but complementary rather than in- 

 compatible, and disharmony results only when they 

 are allowed to mix with one another in verbal state- 

 ments, or when the particular concrete expressions 

 given to the poetic or philosophic activity happen 

 to be at variance with sound science. Between the 

 moods there is no variance. The different moods 

 express different ways of looking at things, and 

 use as it were words of different languages. The 

 evolutionist postulates a beginning somewhere, 

 an initial order of nature instituted in some fashion 

 quite unknown and implying the potentialities of 

 the future in some fashion quite unknown; the 

 creationist gives in non-scientific or transcendental 

 terms some account of the institution of the order 

 of nature; the ideas are not antithetical, they are 

 incommensurable. Moreover, if we may take an- 

 other point of view for a moment, the teaching of 

 the history of science leads us to a strong feeling of 

 gratitude to the deductive or a priori thinkers. They 

 were at least thinking often with a broad perspec- 

 tive and that cannot always be said of researchers. 

 They may have interpolated fanciful ideas where 

 facts alone are decisive, their deductions may have led 

 induction off the scent, they may have blinded vision 

 by preconceptions and deranged reasoning by preju- 

 dices, they may have caused confusion by mixing up 

 objective and subjective terms, and done many other 

 evil things ; but it is a historical fact that astrology 

 led on to astronomy, alchemy to chemistry, cosmolo- 

 gies to geology, and superstitious medical lore to 



