natural selection itself, which in darker moments seemed but a weak agency for sustaining the whole world: ‘If I think continuously on some half-dozen structures of which we can at present see no use, I can persuade myself that natural selection is of quite subordinate importance.’[288] The interesting aspect of this matter of difficulty, as with other things, is Darwin’s way of meeting and facing it. There was an excitement, a stimulus, undoubtedly, a joy in attacking tough problems and conquering them. But there was also a pervading consciousness of what the difficulties were, and some have even thought an almost too pervading disposition to go out of one’s way to deal with them. As Huxley puts it: One ‘who desires to attack Mr. Darwin has only to read his works with a desire to observe not their merits but their defects, and he will find ready to hand more adverse suggestions than are likely ever to have suggested themselves to his own sharpness, without Mr. Darwin’s self-denying aid.’[289] And there is always the appreciation, in handling the difficulties, of the danger in over-ingenuity, of the subtle possibilities of betrayal by reason ever toiling with intense ardor to arrive at its preconceived ends. ‘God knows I have never shirked a difficulty,’ said Darwin.[290] But the danger lies not only in shirking, but in the dissolving, transforming power of prejudice and enthusiasm. Here again Darwin tried to be ever on his guard: ‘I am fairly rabid on the question, and therefore, if not wrong already, am pretty sure to become so.’[291] He would not be misled, or fooled, or betrayed: ‘As I read on, I felt not a little dumbfounded, and thought to myself that whenever I came to this subject I should have to be savage against myself.’[292] But you can never be sure that you have been savage enough, and there are moments when unexpected obstacles make you mistrust your theory, mistrust your method, mistrust your reasoning power. ‘If it could be proved that any part of the structure of any one species had been formed for the exclusive good of another species, it would annihilate my theory.’[293] And who knows that it cannot be proved? After months of study, a clear statement of opposing facts seems for the moment to demolish everything. ‘You give all the facts so clearly and fully, that it is impossible to help speculating on the subject; but it drives me to despair, for I cannot gulp down your continent; and not to be able to do so gives, in my eyes, the multiple creationists an awful triumph.’[294] And with his extraordinary gift of direct self-revelation, Darwin sums up the state of mind in one vivid sentence: ‘Your letter actually turned me sick with panic.’[295]