To be sure, the mention of Voltaire in connection with tolerance rather makes one smile, for if he fought for tolerance as for other things, he fought hard and bitterly, and he was always fighting for something. And in general it may well be urged that the history of scientific thought shows anything but tolerance and gentleness. Indeed it sometimes seems as if scientists were a peculiarly waspish and petulant generation, apt to fly out, and to fly at, with what to the ordinary mind hardly appears sufficient excuse. Darwin himself appreciates this unfortunate tendency, and frequently deplores it: ‘How strange, funny, and disgraceful that nearly all ... our great men are in quarrels in couplets.’[142] But here again, it is human nature, in its inborn weakness and self-satisfaction, that does the quarreling, and the scientific spirit, taken in itself, certainly tends to quiet and lenify. In one of his very latest letters Darwin wrote: ‘You have shown how a man may differ from another in the most decided manner, and yet express his difference with the most perfect courtesy. Not a few English and German naturalists might learn a useful lesson from your example; for the coarse language often used by scientific men towards each other does no good and only degrades science.’[143] But it is difficult for humanity to learn, and when it is learned to remember, the profound truth expressed in the saying of Edmond Scherer in regard to tolerance: ‘The fundamental dogma of intolerance is that there are dogmas, that of tolerance is that there are only opinions.’ And tolerance, the mere recognition that others may be right and we wrong, even as to our most cherished theories, when it is enlightened by clearness of intelligence and warmed by sympathy, easily passes, as we have seen with Darwin in an earlier chapter, into that most delightful of all virtues, or more properly that root of all virtues, the power and the instinct of putting ourselves in others’ places, of entering into their lives. It is not quite enough to respect others’ opinions, or even to defer to them. One should go further, and endeavor to understand how they arrive at them, and to do this, one should be ever alive to the vast community of human nature, and the infinite threads and strands that bind together our hearts and the hearts of even those who appear most different from us. It is this power of comprehension, this effort at comprehension, of others’ point of view, which leads to the wonderful gentleness of tone that makes a great part of Darwin’s charm: ‘You are mistaken in thinking that I ever said you were wrong on any point. All that I meant was that on certain points, and these very doubtful points, I was inclined to differ from you.’[144] It is evident that in arguing, in discussing, Darwin always sought to understand his adversary’s position, and in order to do this, to put himself entirely in his adversary’s place.