The fact that the scientific investigator works 50 percent of his time by nonrational means is, it seems, quite insufficiently recognized. Intuition, like a flash of lightning, lasts only for a second. It generally comes when one is tormented by a difficult decipherment and when one reviews in his mind the fruitless experiments already tried. Suddenly the light breaks through and one finds after a few minutes what previous days of labor were unable to reveal.
