It will be profitable to consider more in detail some specific elements of Darwin’s reasoning. In the first place, we have seen everywhere and in all connections that his propensity to eager theorizing was tempered with an unfailing sense of doubt and mistrust. He was indeed always disposed to act in the spirit of Weisman’s remark: ‘When we are confronted with facts which we see no possibility of understanding save on a single hypothesis, even though it be an undemonstratable one, we are naturally led to accept the hypothesis, at least until a better one can be found.’[371] And he recognized fully the force of the comment which Huxley makes on a phrase of Goethe, to the effect that doubt must not be blighting or destructive, but fruitful and stimulating: ‘Goethe has an excellent aphorism defining that state of mind which he calls “_Thätige Skepsis_”—active doubt. It is doubt which so loves truth that it neither dares rest in doubting nor extinguish itself by unjustified belief.’[64] At the same time, the doubt was there, was temperamental, and could not be altogether extinguished, even when the rush of the logical impetus was fullest. One beautiful expression of it among many is, ‘When you say you cannot master the train of thoughts, I know well enough that they are too doubtful and obscure to be mastered. I have often experienced what you call the humiliating feeling of getting more and more involved in doubt the more one thinks of the facts and reasoning on doubtful points.’[65] The truth is, that Darwin had in a high degree the quality, often so hampering to the man of practical action, but invaluable to the thinker, of getting outside of himself and his own point of view and criticizing it as if it were the standpoint of some one else. He himself indicates this forcibly in connection with returning to one’s ideas after an interval: ‘The delay in this case, as with all my other books, has been a great advantage to me; for a man after a long interval can criticize his own work, almost as well as if it were that of another person.’[66] Some men can.