Indeterminists, Professor Bergson says, must beware, again, of arguing against the prevision of voluntary acts. Once more, this is not because prevision of a voluntary act is possible, but because there is no sense in the phrase. If Paul knew all the conditions under which Peter acts, his imagination would relive Peter’s history. He must pass through Peter’s very own psychic states, to know with precision their intensity and their importance in relation to his other states. The intensity, in fact, is the peculiar quality of the feeling itself. Now, to know _all_ the antecedents of the act would bring you to the act itself, which is their continuation, and not merely their result, and above all in no way separate from them. To relive Peter’s history is just to become Peter--that is the only way Paul could conceivably “know all the antecedents” of the act in question. There is no question of predicting the act, but simply of acting. Knowledge of the antecedents of the act without knowledge of the act is an absurdity, a contradiction. The indeterminists can mean nothing, by such a contention as this, but that the act is not an act until it is acted--which is hardly worth meaning;--and the determinists can mean only that the act, once acted, is acted--which is no better. The subject of freedom is beside the point, in such a debate. So the question of prevision comes to this: Is time spatial? You drew Peter’s states, you perceived his life as a marking in space. You then rubbed out, in thought, the part OA, and asked if, knowing the part before O, you could have determined OA beforehand. That is the question you put when you bring in Paul’s representation of the conditions (and therefore their materialization) under which Peter shall act. After having identified Paul with Peter, you make Paul take his former point of view, from which he now sees the line MOA complete, having just traced it in the rôle of Peter. Prevision of natural phenomena has not the slightest analogy with that of a voluntary act. Time, in scientific formulæ, is always and only a number of simultaneities. The intervals may be of any length; they have nothing to do with the calculation. Foreseeing natural phenomena is making them present, or bringing them at least enormously nearer. It is the intervals, the units themselves--just what the physicist has nothing to do with--that interest the psychologist. A feeling half as long would not be the same feeling. But when one asks if a future action can be foreseen, one identifies physical time, which is a number, with real psychological duration, which has no analogy with number. In the region of psychological states there is no appreciable difference between foreseeing, seeing and acting.