For Paul to foretell Peter's act, Paul would simply have to become Peter. [Footnote: Time and Free Will, p. 187 (Fr. p. 144).] The very reasons which render it possible to foretell an astronomical phenomenon are the very ones which prevent us from determining in advance an act which springs from our free activity. For the future of the material universe, although contemporaneous with the future of a conscious being, has no analogy to it. The astronomer regards time from the point of view of mathematics. He is concerned with points placed in a homogeneous time, points which mark the beginning or end of certain intervals. He does not concern himself with the interval in its actual duration. This is proved by the fact that, could all velocities in the universe be doubled, the astronomical formulae would remain unaffected, for the coincidences with which that science deals would still take place, but at intervals half as long. To the astronomer as such, this would make no difference, but we, in ourselves, would find that our day did not give us the full experience. Situations which arose as a result of the introduction of "summer time" serve to make this point clear. As then we find that time means two different things for the astronomer and the psychologist, the one being concerned with the points at the extremities of intervals, and the other with the enduring reality of the intervals themselves, we can see why astronomical phenomena are capable of prediction and see too that, for the same reason, events in the realm of human action cannot be so predicted and therefore the future is not predetermined but is being made.