But Science does not yet understand, nor does it pretend to understand, the enigma. Like all previous systems of knowledge, it fails to detect the actual concatenation, the necessary connection or continuous transition, by which these two seemingly heterogeneous experiences are bound together and unified in reality. It does not conceive how motion can possibly generate sensation, or indeed how motion and sensation can in any way be related to each other. Yet, to the vindication of the hypothesis of evolution, it is quite indispensable to establish either the essential identity of motion and sensation, or the gradual transformation of one of these modes of existence into the other. For how can evolution maintain its pretensions to universality, if the ideal world remains foreign to it—a mysteriously correlated entity, merely in close correspondence with the outer world, but having with it no genuine and intrinsic sameness of actuality?
The penetration and elucidation of this ancient dilemma of motion and sensation would furnish the data for the solution of what may be called the psychical phase of the problem of life.
But intermediate between these two extreme aspects of the problem the one demanding the explanation of the origin of vitality and organization; the other the proof of the identity or direct phenomenal continuity of motion and sensation—there is disclosed by the requirements of the evolution hypothesis a third essential and very peculiar aspect of the same problem. As the experience of sensation, the state of so-called feeling is an exclusive attribute of vitality; it is evident that, granting the evolution hypothesis, feeling must make its appearance and take its rise at some definite moment in the course of organization. The demonstration of the specific conditions of organization, which constitute the starting-point of feeling or subjective experience, would furnish the initial data for the solution of what we may call the physico-psychical phase of the problem of life.
We have now gained some information regarding the ground which has to be accurately explored before the hypothesis of continuous development can be said to be adequately established. Having indicated the exact points at which our scientific appreciation meets with the most abrupt and startling breaks in the supposed continuity, we find ourselves in a favorable position to estimate what, above all, has to be accomplished before evolution can take the field as a consistent monistic system.
We have to show how life originates and how organization takes its rise; we have to demonstrate how in the course of organic development the state which we call feeling is established; and we have, finally, to prove that this feeling is in essence identical with that which is felt. How are we to set about this seemingly hopeless and endless task? Are we to rummage the vast stores of accumulated facts in search of the missing links? Assuredly, had they been forged and ready for the purpose, more competent and assiduous searchers would have discovered them long ago.