I sincerely hope that I shall not be accused of Pyrrhonism, or of any desire to weaken the foundations of rational certainty. I have merely desired to point out that rational certainty is one thing, and talk about "impossibilities," or "violation of natural laws," another. Rational certainty rests upon two grounds; the one that the evidence in favour of a given statement is as good as it can be; the other, that such evidence is plainly insufficient. In the former case, the statement is to be taken as true, in the latter as untrue; until something arises to modify the verdict, which, however properly reached, may always be more or less wrong, the best information being never complete, and the best reasoning being liable to fallacy. To quarrel with the uncertainty that besets us in intellectual affairs would be about as reasonable as to object to live one's life, with due thought for the morrow, because no man can be sure he will be alive an hour hence. Such are the conditions imposed upon us by nature, and we have to make the best of them. And I think that the greatest mistake those of us who are interested in the progress of free thought can make is to overlook these limitations, and to deck ourselves with the dogmatic feathers which are the traditional adornment of our opponents. Let us be content with rational certainty, leaving irrational certainties to those who like to muddle their minds with them. [As for the difficulty of believing miracles in themselves, he gives in this paper several examples of a favourite saying of his, that Science offers us much greater marvels than the miracles of theology; only the evidence for them is very different. The following letter was written in acknowledgment of a paper by the Reverend E. McClure, which endeavoured to place the belief in an individual permanence upon the grounds that we know of no leakage anywhere in nature; that matter is not a source, but a transmitter of energy; and that the brain, so far from originating thought, is a mere machine responsive to something external to itself, a revealer of something which it does not produce, like a musical instrument. This "something" is the universal of thought, which is identified with the general logos of the fourth gospel. Moral perfection consists in assimilation to this; sin is the falling short of perfect revealing of the eternal logos. Huxley's reply interested his correspondent not only for the brief opinion on the philosophic question, but for the personal touch in the explanation of the motives which had guided his life-work, and his "kind feeling towards such of the clergy as endeavoured to seek honestly for a natural basis to their faith." Hodeslea, Eastbourne, March 17, 1891. Dear Mr. McClure, I am very much obliged for your letter, which belongs to a different category from most of those which I receive from your side of the hedge that, unfortunately, separates thinking men.