THE UNITY OF SCIENCE 31 



plete unification thus imply a denial of all physical efficacy to 

 thoughts and feelings as such. Those, on the contrary, who 

 assert such efficacy deny by implication the possibility of a 

 complete unification of even the laws of the motion of matter. 

 They tacitly or explicitly introduce a real discontinuity into the 

 fabric of science. 



They introduce, however, only one discontinuity ; and that 

 is a long- familiar one, and one that comes at a point rather 

 high up in the scale of phenomena. It is interesting to ob- 

 serve that in some of the recent tendencies of which I have 

 spoken in vitalism, for example, and in 'scientific plural- 

 ism' in general we find other discontinuities in scientific law 

 introduced at points lower in the series. What, then, is the 

 issue at stake in this more extensive denial of the possibility 

 of unification? Its significance is obviously not the same as 

 that which inheres in the question of the efficacy of thought; 

 for it asserts more than the discontinuity implied by the ef- 

 ficacy of thought. We shall perhaps best see the bearing of 

 the assertion if we recall the fact that our sequence of sciences 

 can be arranged not only in a scale of so-called complexity, 

 but also in the chronological order of the classes of phenomena 

 to which the several sciences refer. In the evolution of our 

 solar system and planet there was perhaps a time when a 

 chemist as such if we can imagine a disembodied, a seraphic 

 chemist, hovering above the spectacle would have found his, 

 occupation not yet pertinent. For it is, I suppose, now prob- 

 able that our present chemical elements were themselves 

 evolved from a smaller number of substances and perhaps 

 from a primeval undifferentiated 'protyle'. As evolution went 

 on, chemical phenomena must have appeared and the laws of 

 chemical combination been in observable operation ; but for 

 seraphic biologists there would even yet have been no employ- 

 ment, since there were no organisms and therefore no ex- 

 emplifications of specifically biological laws. And when 

 biological phenomena first appeared with the plants, there 

 must, probably, still pass many ages before consciousness came 



