Let us refer back to the analysis of thinking given in the case of the man who discovered footprints on the beach. Even there, in order to give any adequate idea of his thought process, I was obliged to show that for various reasons he rejected certain suggested solutions. But this negative method could be more fully developed. Because the man rejected a certain solution, it does not follow that it was necessarily wrong. Suppose the final suggestion—that the unknown had been on the island all the time—were to have been tested out, and that certain further facts were discovered which tended to disprove it; the man might find it necessary to look for still another solution. But suppose this were not forthcoming, suppose that all the possibilities had been exhausted. It would be necessary to return to some of the original suggestions. He would have to see whether an error had been made in testing them. In rejecting the suggestion of a small boat he may have overestimated the distance of this island from other land. He may have underestimated the difficulties that a man in a small boat is capable of surmounting. In rejecting the supposition of a ship, he may have erred in his judgment of the time the footprints had been on the beach, or of the time it would take a large vessel to get out of sight. What is essential is that all suggestions be tested out, either by memory, observation or experiment, in all their implications, and that the tendency be resisted to accept the first solution that suggests itself. For the uncritical thinker will always jump at the first suggestion, unless an objection actually forces itself into view. Remaining in a state of doubt is unpleasant. The longer the doubt remains the more unpleasant it becomes. But the man who is willing to accept this unpleasantness, the man who is willing carefully to observe, or experiment if need be, to test the validity of his suggestions, will finally arrive at a solution much deeper, and one which will give him far more satisfaction, than the superficial answer obtained by the man of careless habits of thought. Thomas A. Edison says he always rejects an easy solution of any problem and looks for something difficult. But the inventor has one great advantage over any other kind of thinker. He can test his conclusion in a tangible way. If his device works, his thinking was right; if his device doesn’t work, his thinking was wrong. But the philosopher, the scientist, the social reformer, has no such satisfactory test. His only satisfaction is the feeling that his results harmonize with all his experience. The more critical he has been in arriving at those results, the more deep and permanent will be that feeling, the more valuable will be his thoughts to himself and to the world. . . .