We now have the essence of Professor James's case, and can consider it in detail. First of all we may note the curiously double sense in which Professor James uses the word "fact" and the agility with which he skips from one meaning to another, as it suits his argument. In a broad and general sense a mental fact is as much a fact as any other fact. A man riding on horseback is a fact. My vision or conception of a horse with the head of a man is equally a fact, though nothing like it exists in nature. We should discriminate between the two by saying that one is a mental fact strictly relative to a particular mind, the other is an objective fact relative to all minds normally constituted. Now science does not deny possibilities as _mental facts_. But it would be a very queer science indeed that allowed all sorts of possibilities of a given group of phenomena _under identical conditions_. Like "chance," the possibilities of the Universe are strictly relative to our knowledge concerning it. If opposite things appear equally possible, it is only because we are not sufficiently conversant with the processes to say which thing is certain. A universe with Professor James walking down Divinity Avenue appears as orderly and as natural as one with him parading Oxford Street. But this is because we cannot unravel the complex conditions that may determine the selection of one route or the other. Or if it be said in reply, that the walker is unaware of any choice in the matter, the answer is that there is present the desire to get away from the lecture hall and arrive at home, and this is strong enough to make the choice of means to that end unimportant. If the choice lay between walking down a sunlit street or wading through a mile of water, five feet deep, while the latter would still remain a possibility, since it could be done were the inducement to do it strong enough, there is not much doubt as to what the choice would actually be.