exists, though it is not such as an old-fashioned intellectualist psychology would have supposed. Although I shall not discuss it, we shall do well to bear it in mind, in order to realise that our discussions may have bearings upon matters lying outside the sphere of pure intellect.
I mentioned a moment ago three defects in common beliefs, namely, that they are cocksure, vague, and self-contradictory. It is the business of philosophy to correct these defects so far as it can, without throwing over knowledge altogether. To be a good philosopher, a man must have a strong desire to know, combined with great caution in believing that he knows; he must also have logical acumen and the habit of exact thinking. All these, of course, are a matter of degree. Vagueness, in particular, belongs, in some degree, to all human thinking; we can diminish it indefinitely, but we can never abolish it wholly. Philosophy, accordingly, is a continuing activity, not some thing in which we can achieve final perfection once for all. In this respect, philosophy has suffered from its association with theology. Theological dogmas are fixed, and are regarded by the orthodox as incapable of improvement. Philosophers have too often tried to produce similarly final systems: they have not been content with the gradual approximations that satisfied men of science. In this they seem to me to have been mistaken. Philosophy should be piecemeal and provisional like science; final truth belongs to heaven, not to this world.
The three defects which I have mentioned are interconnected, and by becoming aware of any one we may be led to recognise the other two. I will illustrate all three by a few examples.
Let us take first the belief in common objects, such as tables and chairs and trees. We all feel quite sure about these in ordinary life, and yet our reasons for confidence are really very inadequate. Naïve common sense supposes that they are what they appear to be, but that is impossible, since they do not appear exactly alike to any two simultaneous observers; at least, it is impossible if the object is a single
