The power of reason is thought small in these days, but I remain an unrepentant rationalist. Reason may be a small force, but it is constant, and works always in one direction, while the forces of unreason destroy one another in futile strife. Therefore every orgy of unreason in the end strengthens the friends of reason, and shows afresh that they are the only true friends of humanity.

The objection to propaganda is not only its appeal to unreason, but still more the unfair advantage which it gives to the rich and powerful.

It is not what the man of science believes that distinguishes him, but how and why he believes it. His beliefs are tentative, not dogmatic; they are based on evidence, not on authority or intuition.

I do not pretend to be able to prove that there is no God. I equally cannot prove that Satan is a fiction. The Christian god may exist; so may the gods of Olympus, or of ancient Egypt, or of Babylon. But no one of these hypotheses is more probable than any other: they lie outside the region of even probable knowledge, and therefore there is no reason to consider any of them.

All that alcohol does for them is to liberate the sense of sin, which reason suppresses in saner moments.

The methods of increasing the degree of truth in our beliefs are well known; they consist in hearing all sides, trying to ascertain all the relevant facts, controlling our own bias by discussion with people who have the opposite bias, and cultivating a readiness to discard any hypothesis which has proved inadequate.

The difficulty is that, so long as unreason prevails, a solution of our troubles can only be reached by chance; for while reason, being impersonal, makes universal co-operation possible, unreason, since it represents private passions, makes strife inevitable. It is for this reason that rationality, in the sense of an appeal to a universal and impersonal standard of truth, is of supreme importance to the well-being of the human species.

The fact is you cannot be intelligent merely by choosing your opinions. The intelligent man is not the man who holds such-and-such views but the man who has sound reasons for what he believes and yet does not believe it dogmatically. And opinions held for sound reasons have less emotional unity than the opinions of dogmatists because reason is non-party, favouring now one side and now another. That is what people find so unpleasant about it.

For my part, I prefer the ontological argument, the cosmological argument and the rest of the old stock-in-trade, to the sentimental illogicality that has sprung from Rousseau.