Chapter 11

'Corollary I' —
Granted the existence of transient acts,
we can demonstrate the existence of God

1226. An extremely important corollary can be drawn from the definition we have given. Here, I want to comment on this corollary which we shall need as we go on if we are to proceed with total clarity and distinction of thought.
This corollary concerns the existence of God, demonstrated only from the existence of transient acts. To my mind, the demonstration is utterly clear, and can be set out as follows.

If transient acts exist, immanent acts also exist; the former are only the beginning or termination of the latter. But no immanent act can be the cause of its own termination because no act can be the cause of its own non-act, that is, of its own cessation. Nor can the immanent act be the cause of its own beginning because no act can give itself existence. If it did, it would act before it was.

Now, the transient act also needs a cause because it is change, passage. It needs a cause according to the principle of cause.(121) Nor can this cause be the transient act itself. As I said, that which is not, cannot give itself existence.
But if the transient act is not caused by an immanent act whose beginning and end it is, there must be another immanent act which causes it.
This immanent act which causes the transient act will either itself begin, in which case it would be caused by a transient act, or it will have no beginning of any kind and hence no end.

If it is caused by a transient act, we shall have to go back to another immanent act. But to avoid seeking causes ad infinitum (in which case no act would be produced because an infinite time, which is never traversed, would be needed to produce it), we have to stop at an immanent act which has neither beginning nor end. If, then, this act is not caused by a transient act, we have again an immanent act without beginning and without end. An immanent act exists, therefore, without beginning and without end; and this is God.

If, therefore, transient acts exist, Almighty God necessarily exists.(122)

1227. This demonstration of the existence of God has the advantage of leading directly to God as immanent act, and totally pure act.

Notes

(121) NE , vol. 2, 567.

(122) The demonstration of the existence of God from motion, which St. Thomas took from Aristotle, Physics , 7 and 8, and is, he says, 'The first and most obvious way of demonstrating the divine existence' (S.T. , I, q. 2, art. 3), receives its force from the principles we have given about the nature of immanent and transient acts.