THF UNITY OF SCIENCE 9 



edge. It has accordingly tended to encourage a very old hope 

 of many philosophers and scientific investigators, that of the 

 eventual reduction of all the sciences to one, the interpreta- 

 tion of all phenomena in terms of a single general type of 

 phenomenon and the description of all of them in terms of 

 relatively few, fundamental, all-comprehensive laws. As our 

 knowledge of nature both broadens and deepens, the sciences 

 appear more intimately and intricately interlaced near their 

 roots ; and the question suggests itself whether they have not 

 in fact a common tap-root. It is, therefore, of especial in- 

 terest at the present juncture in the history of science to in- 

 quire how far this obliteration of divisions has gone, in what 

 degree an actual unity or continuity has been realized, how 

 reasonable these hopes for ultimate complete unification ap- 

 pear in the light of existing knowledge. Upon these ques- 

 tions all of the lectures which are to follow will have some- 

 thing to say by implication, even though none of the lecturers 

 should discuss directly any such topic. But in order that this 

 bearing of the course as a whole may more clearly appear, it 

 is perhaps well that this prefatory discourse should be de- 

 voted to a highly-generalized and provisional formulation of 

 the questions : how far the several sciences constitute a 

 single system ; how far they are merely a collection of separate 

 and independent bodies of knowledge ; and of what sort, in 

 any case, are the logical relations between them, 



Now, 'one' in some sense the sciences certainly are; it 

 is, as has been said, one of the purposes of this course to ex- 

 hibit and emphasize that unity. But it is quite possible to 

 talk about the unity of knowledge in a very vague and equiv- 

 ocal way, and, indeed, in a rather superstitious and canting 

 way — a thing which was a good deal done, I think, in con- 

 nection with the great cecumenical council of scholars which 

 was held in St. Louis during the World's Fair of 1904. For 

 unity is a highly ambiguous term; and there are certain 

 senses in which its application to the sciences as a whole is 

 obvious but not very important, and other senses in which 



