(1) The refutation of any argument against the Faith is not a demonstration of the truth of the Faith. It is the removal only of an obstacle to the Faith. For the Faith is not arrived at by demonstration, but by demonstration it is shown to be at least tenable. The Faith is not a conclusion which all can reach by the formal action of reason, but a revelation to be defended by reason. The Faith is not a theory, but a thing. It is rational, but not deductively arrived at. There is no process whereby all mankind can be convinced of it as of an abstract proposition. But there is a process whereby all mankind can be convinced that each particular proposition against it has failed. This principle in what is called “Apologetics” (that is, writings in defence of Catholic truth) is so generally neglected that it is of the first importance to make it quite clear at the opening of any discussion upon revealed religion. A man who can see colours will never be able to prove colour to a colour-blind man. He can show that the colour-blind man’s arguments--e.g., that colours do not exist because if they did they would affect surface--are false. If he proceeds to establish the presence of colours positively, he must do so by analogy, by convergent evidence, by the manifest action of others, by the proved nature of other senses than that of sight. He can only _prove_ (in the strict deductive sense of the word “prove”) that the sense of colour is rational, acceptable without violence to the human mind; but that it is present he must establish by other methods. Nearly all our modern debates in this matter are confused by the fact that one of the parties misconceives the nature of these debates. The opponent of Catholicism thinks that its apologist is, in arguing, trying to prove Catholic truth as one proves a case for a positive verdict. He is not. He is rebutting the supposed value of opposing evidence; he is pleading for a negative verdict; for acquittal of the charge “irrational.” When he comes to establishing the Faith positively, he does not do so by following one line of deductive reason, but by a mass of converging considerations. History cannot be said to prove the Faith, save in the very extended use of the word “prove” to mean a general process of increasing conviction from the examination of what is revealed of the Church’s action on the world, of men’s attitude towards it, of the moral and intellectual activities of acceptors and rejectors compared. But it can be _proved_ that an increasing knowledge of History does not shake the Church’s claim to Divine Authority: while, on the contrary, a lesser knowledge is almost invariably more hostile to that authority than a greater. (2) I have used the term “reason,” and this leads me to my second premise: The human reason is absolute in its own sphere.