From a distribution of over six hundred copies of a set of questions upon this subject, I have received one hundred and two answers, largely from professional men and women, and from the students of the upper classes of our leading American colleges, each paper subscribed with the name, age, and address of the sender. In obtaining this mass of material, I have been placed under great obligations to President McCosh; to Professor George P. Fisher, of Yale College; Professor William James, of Harvard College; President Robinson, of Brown; Professor Osborn, of Princeton; Professor Stanley Hall, of Johns Hopkins; Dr. Nicholas Murray Butler, of Columbia; and Professor Torrey, of the University of Vermont. The healthy, normal side of this subject is the only one I shall attempt to consider, leaving the questions of morbid pathology to those who alone can weigh the evidence it throws upon the subject.
If, in our experience, we witness an effect, we know, by the inexorable logic of science, that its existence must be due to some efficient cause. "Verily a tree is known by its fruit" is sound teaching and sound sense—it is axiomatic. If a solution of a mathematical problem can really be revealed to us in consciousness, while we are busied about other things, it must inevitably have been performed by means of the processes which regularly lead to such a result, even if we are not conscious at the time of employing such processes. It could not have come spontaneously, but only as the result. As a consequence, in such a case we would be bound to predicate some exercise of intellectual powers, actively working during unconsciousness. The circular before referred to comprised eleven questions; those, the results of which are specially used here, are as follow:
"2. "When you are, do you feel some trouble or weight in your effort?
"3. When you are not, does the idea ever, when it occurs, seem to have come back spontaneously, without being suggested by any perceived association of ideas?"
Third Question.—"During sleep, have you ever pursued a logical, connected train of thought upon some topic or problem in which you have reached some conclusion, and the steps and conclusions of which you have remembered on awakening?"
Sixth Question.—"1. Can you wake precisely at a given hour, determined upon before going to sleep, without waking up many times before the appointed time?
"2. If you can, then (a) is this habitual, or do you often fail? (b) Are you conscious, before waking, of any feeling? (describe it), or (c) do you come directly from oblivion into consciousness?"
Ninth Question.—"When perplexed at your progress in any work (mathematical, professional, literary, chess, puzzles, etc.), have you ever left it unfinished and turned your attention to other things, and, after some time, on voluntarily returning to it, have found yourself able at once to satisfactorily master it?"
