To appreciate fully Darwin’s combination of mental activity and fertility with moderation and restraint, it is well to place him between two extreme types of thinkers. On the one hand, there is the born essential reasoner, and logician, Spinoza, for instance, or Hegel, or Darwin’s own contemporary, Spencer, the man who to a greater or less extent takes fact for his foundation, but who by nature and temperament delights to weave an elaborate web of logical theory, rigid and perfect in its appearance of systematic deduction, but too apt in the end to treat facts with indifference if not disrespect. I like especially in this regard to compare Darwin with Lucretius. The _De Rerum Natura_ is one of the most striking, enthralling examples of what I should call passionate thinking. Theoretical problems take hold of Lucretius like the ecstasies of love. He tears and wrenches at the roots of thought, determined to make them yield to the delving vigor of his eager search. Now Darwin has a broad and constant curiosity, his interest may well be called enthusiasm, and he himself uses the term passion for it: ‘Hence it has come to be a passion with me to try to connect all such facts by some sort of hypothesis.’[461] Yet in no phase of his nature should I be inclined ever to employ the general word, ‘passion,’ and it seems to me that every page of Lucretius is stamped with a devouring ardor different from anything Darwin knew. On the other hand, over against these furious reasoners, I should set Darwin’s close contemporary, Sainte-Beuve, who, as I said in the previous chapter was, in some aspects, as admirable a representative of the scientific spirit as Darwin himself. The endless curiosity, the unlimited observation of fact, as embodied in the human subject, have never been more richly exemplified than in the great French critic. But Sainte-Beuve was no reasoner in the larger sense. He did not even avoid reasoning from mistrust: he had no taste for it, and when he dealt with it, it was always charily and with extreme reserve. He delighted to study and portray individuals and to allow those individuals, as it were, to classify themselves and so to point the way to general results. Between these two extremes Darwin stands, as one who used reasoning to the fullest extent for the interpretation of fact, yet at the same time always stuck closely and rigidly to the fact itself, and would not allow it to be for an instant distorted by the reasoning process. II