It results from their periodicity that, in men of genius, sterile years precede productive years, these again to be followed by sterility, the barren periods being marked by psychological self-depreciation, by the feeling that they are less than other men; times in which the remembrance of the creative periods is a torment, and when they envy those who go about undisturbed by such penalties. Just as his moments of ecstasy are more poignant, so are the periods of depression of a man of genius more intense than those of other men. Every great man has such periods, of longer or shorter duration, times in which he loses self-confidence, in which he thinks of suicide; times in which, indeed, he may be sowing the seeds of a future harvest, but which are devoid of the stimulus to production; times which call forth the blind criticisms “How such a genius is degenerating!” “How he has played himself out!” “How he repeats himself!” and so forth. It is just the same with other characteristics of the man of genius. Not only the material, but also the spirit, of his work is subject to periodic change. At one time he is inclined to a philosophical and scientific view; at another time the artistic influence is strongest; at one time his intervals are altogether in the direction of history and the growth of civilisation; later on it is “nature” (compare Nietzsche’s “Studies in Infinity” with his “Zarathustra”); at another time he is a mystic, at yet another simplicity itself! (Björnson and Maurice Maeterlinck are good modern examples.) In fact, the “amplitude” of the periods of famous men is so great, the different revelations of their nature so various, so many different individuals appear in them, that the periodicity of their mental life may be taken almost as diagnostic. I must make a remark sufficiently obvious from all this, as to the existence of almost incredibly great changes in the personal appearance of men of genius from time to time. Comparison of the portraits at different times of Goethe, Beethoven, Kant, or Schopenhauer are enough to establish this. The number of different aspects that the face of a man has assumed may be taken almost as a physiognomical measure of his talent.[9] [9] I cannot help using the word “talent” from time to time when I really mean genius; but I wish it to be remembered that I am convinced of the existence of a fundamental distinction between “talent,” or “giftedness,” and “genius.” People with an unchanging expression are low in the intellectual scale. Physiognomists, therefore, must not be surprised that men of genius, in whose faces a new side of their minds is continually being revealed, are difficult to classify, and that their individualities leave little permanent mark on their features.