[125] Under the title _Zur Entwickelung von Kant’s Theorie der Naturcausalität_, (_Philosophische Studien_, IX, 3 and 4), Wundt gives us a rapid historical sketch. He holds that speculation, in antiquity, is characterised by the method of contraries: the opposition of being and becoming, etc. It is wholly qualitative. The ancients progressed by definition. Elaboration of the concept of mechanical causation was impossible, by reason of the absence of any quantitative determination. This began with Galileo. The progress of mathematics, and the introduction of fractional and irrational numbers made it possible to search out, not merely measure, but also the relation between magnitudes—i. e., _function_. This became the type, and at the same time the goal of all intellectual elaboration, as applied to natural phenomena. This method culminated in the seventeenth century, with the predominance of the logical type. In consequence of the old concept of substance, forces were taken as cause, phenomena as effect. The latter is more frequently derived from cause by deduction, not by intuition. The cause of a determined event might either be the total of its conditions, or one antecedent event. This last conception prevailed, as being the more favorable to the application of mathematics. The eighteenth century marks the genesis of the biological sciences. The growing importance of observation and experimental research made against the preponderance of mathematics. The facts of experience were held more solid than the conclusions of reason. The type of causality is placed no longer in deduction, but in sensory intuition; it is the residuum of experience. This tendency found its exponent in Hume. Kant endeavored to reconcile the two theses; that which models object upon subject (seventeenth century) and that which models subject upon object (eighteenth century). [126] 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. [127] W. James, _Psychology_, II., p. 671.