expectation for the present and future.  We find, practically, that expectations, based upon careful observations of past events, are, as a rule, trustworthy.  We should be foolish indeed not to follow the only guide we have through life.  But, for all that, our highest and surest generalisations remain on the level of justifiable expectations; that is, very high probabilities.  For my part, I am unable to conceive of an intelligence shaped on the model of that of men, however superior it might be, which could be any better off than our own in this respect; that is, which could possess logically justifiable grounds for certainty about the constancy of the order of things, and therefore be in a position to declare that such and such events are impossible.  Some of the old mythologies recognised this clearly enough.  Beyond and above Zeus and Odin, there lay the unknown and inscrutable Fate which, one day or other, would crumple up them and the world they ruled to give place to a new order of things.

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.