There are many such records from men of genius. At the moment the inventor obtains the solution of his problem his mind may seem to be least engaged with it. The long-sought-for idea comes like an inspiration, something freely imparted rather than voluntarily acquired. No mental process is more worthy to command respect; but it may not lie beyond the possibility of explanation. Like ethical insight, or spiritual illumination, the scientific idea comes to those who have striven for it. The door may open after we have ceased to knock, or the response come when we have forgotten that we sent in a call; but the discovery comes only after conscious work. The whole history of science shows that it is to the worker that the inspiration comes, and that new ideas develop from old ideas.
It may detract still further from the mysteriousness of the discovery-process to add that the illuminating idea may come in the midst of conscious work, and that then also it may appear as a sudden gift rather than the legitimate outcome of mental effort. The spontaneity of wit may afford another clue to the mystery of scientific discovery. The utterer of a witticism is frequently as much surprised by it as the auditors, probably because the idea comes as verbal imagery, and the full realization of their significance is grasped only with the actual utterance of the words. The fact that to the scientific discoverer the solution of his problem arrives at the moment when it is least sought is analogous to the common experience that the effort to recall a name may inhibit the natural association.
The tendency to emphasize unduly the rôle played by the scientific imagination springs probably from the misconception that the imagination is a psychological superfluity, one of the luxuries of the mental life, which should not be withheld from those who deserve the best. The view lingers with regard to the æsthetic imagination. James could not understand the biological function of the æsthetic faculty. On the alleged uselessness of this phase of the human mind A. J. Balfour has recently based an argument for the immortality of the soul. This view is strikingly at variance with that which inclines to identify it with that mental process which creates scientific theories and thus paves the way for the adjustment of posterity to earthly conditions.