Note 12 — THE CLASSIFICATION OF THE SCIENCES.

Perhaps some will say that such incidental phenomena as those of the heat and light evolved during chemical changes, are to be included among chemical phenomena. I think, however, the physicist will hold that all phenomena of re-distributed molecular motion, no matter how arising, come within the range of Physics. But whatever difficulty there may be in drawing the line between Physics and Chemistry (and, as I have incidentally pointed out in The Principles of Psychology, § 55, the two are closely linked by the phenomena of allotropy and isomerism), applies equally to the Comtean clas­si­fi­ca­tion, or to any other. And I may further point out that no obstacle hence arises to the clas­si­fi­ca­tion I am defending. Physics and Chemistry being both grouped by me as Ab­stract-Con­crete Sciences, no difficulty in satisfactorily dividing them in the least affects the sa­tis­fac­tor­i­ness of the division of the great group to which they both belong, from the other two great groups.