greater practical value than Spencer's principle. They are quantitative while the other is but qualitative, and so, while in simple cases it is possible to make specific deductions from these, nothing of the kind has ever been accomplished with the aid of the formula of evolution. Let us imagine a law of gravitation, robbed of its quantitative element, to read: "Every particle of matter attracts every other particle of matter." Such a principle would be true, but much of its practical value would have disappeared. Without going all the way to the pragmatist position, we must at least admit that a law, from which no practical deductions can be made, is one which we can only note and put on the shelf till it is possible to make use of it. There are, however, two considerations which should not be overlooked in assessing its value. A qualitative proposition may be a necessary stepping stone to a fuller and quantitative statement of the truth it contains; and again, because no practical deductions have been made from a universal principle, it does not therefore follow that valuable deductions may not be discovered in the future.
Even if we apply the pragmatist test in its crudest form, Spencer's principle will not be found to have been entirely barren, and it finds special interest in the fact that its applicability is greatest in precisely those branches of knowledge where the other great physical principles are so entangled with other factors that they afford us very little help in unravelling the complexity. Readers, for example, of Professor Sully's work on psychology[1] (to say nothing of Spencer's own works) cannot but admit that, even in psychology, Spencer's principles of differentiation and integration are of some value. In biology and in sociology Spencer has pointed out examples too numerous to mention. Again, in speculation on the largest aspects of the cosmic process of change, it is not a small thing to possess even one conception which pervades all nature.
Like every other great principle, it will serve us well so long as we do not expect too much of it. A law of the highest degree of abstractness will not by itself give particular conclusions, it
- ↑ The Human Mind, by Prof. James Sully, particularly chapter 7.
