As regards this world, in questions of morals, of conduct, and generally of the bearing of evolution on sociology, Darwin’s own sturdy moral habit and self-poised temperament made him perhaps unduly optimistic. Temptation had little hold upon him. Why should it have more upon others, even unsustained by celestial guidance and control? In ‘The Descent of Man’ he endeavors to show the social instinct as a sufficient and satisfactory basis for upright living: ‘We have seen that even at an early period in the history of man, the expressed wishes of the community will have naturally influenced to a large extent the conduct of each member.... Thus the reproach is removed of laying the foundation of the noblest part of our nature in the base principle of selfishness.’[163] And elsewhere he adds, ‘It is not improbable that after long practice virtuous tendencies may be inherited.’[164] Yet the deadly, grinding, destroying implications of the struggle for existence do crop out everywhere, and the best intentioned efforts do not altogether disguise them: ‘It may be difficult, but we ought to admire the savage instinctive hatred of the queen-bee, which urges her to destroy the young queens, her daughters, as soon as they are born, or to perish herself in the combat; for undoubtedly this is for the good of the community; and maternal love or maternal hatred, though the latter fortunately is most rare, is all the same to the inexorable principle of natural selection.’[165] While Darwin’s optimism as to possible consequences appears, it seems to me, in a note to the ‘Descent.’ He is commenting on an article of Miss Cobb, in which she says, referring to his ethical explanations, ‘I cannot but believe that in the hour of their triumph would be sounded the knell of the virtue of mankind.’ On which Darwin remarks comfortably, ‘It is to be hoped that the belief in the permanence of virtue on this earth is not held by many persons on so weak a tenure.’[166] When it comes to the bearing of evolution on another world, Darwin’s attitude is equally interesting, and equally inconclusive. To me one of the most characteristic and suggestive sentences he ever wrote occurs in a letter to Wallace, of August, 1872 (italics mine): ‘Perhaps the mere reiteration of the statements given by Dr. Bastian and by other men, whose judgment I respect, and who have worked long on the lower organisms, would suffice to convince me. Here is a fine confession of intellectual weakness; but _what an inexplicable frame of mind is that of belief_.’[167] The implications here are almost fathomless, but it is clear enough that to Darwin belief in general was not a spiritual necessity of his being, but merely came with the overwhelming obtrusion of fact.