Note 126 — Chapter V · EVOLUTION OF THE PRINCIPAL CONCEPTS.

The question is sometimes raised as to whether psychical (and consequently moral, social) facts ought to be included under the formula of conservation of energy and correlation of forces. Since the only evidence produced has been of the nature of theoretical affirmations, or vague and partial experiences, without quantitative determination, the question so far remains open. The concept of natural causality was in the same way considered above in its positive sense, i. e., as a relation of invariable sequence, without inquiring whether it extends to all forms of experience,—or whether it is limited.