What, now, is the insuperable dilemma which Professor James places before upholders of Determinism? The whole of it turns out to be little more than a play upon the words "possible" and "actual." Determinism, he says, professes that "those parts of the universe already laid down absolutely appoint and decree (Why 'appoint' and 'decree'? Why not the impersonal word 'determine?') what the other parts shall be." The future is determined by the past; and given the past, only one future is possible. Indeterminism says that "the parts have a certain amount of loose play on one another, so that the laying down of one of them does not necessarily determine what the others shall be." Thus, still following Professor James's exposition, given a special instance, both sides admit the occurrence of a volition. The Determinist asserts that no other volition could have occurred. The Indeterminist asserts that another volition might have occurred, other things remaining the same. And, asks the Professor, can science tell us which is correct? His reply is, No. "How can any amount of assurance that something actually happened give us the least grain of information as to whether another thing might or might not have happened in its place? Only facts can be proved by other facts. With things that are possibilities and not facts, facts have no concern." The position may be made clearer by taking the Professor's own illustration. When, he says, I leave this lecture hall I may go home _via_ Divinity Avenue, or traverse Oxford Street. It is a matter of chance which route is selected. But assume that by some miracle, after having walked down Divinity Avenue, ten minutes of time are annihilated, and reaching the Hall door again Oxford Street is the route selected. Spectators thus have two alternative universes. One universe with the Professor walking through Divinity Avenue, the other with him walking through Oxford Street. If the spectators are Determinists they will believe only one universe to have been from eternity possible. But, asks Professor James, looking outwardly at these two universes, can anyone say which is the accidental and which is the necessary one? "In other words, either universe _after the fact_ and once there would, to our means of observation and understanding, appear just as rational as the other." There is no means by which we can distinguish chance from a rational necessity. A universe which allows a certain loose play of the parts is as rational as one which submits to the most rigid determinism.