Origin

In the Beginning has a distinction between "beginnings" and "origin" that is interesting to think about though perhaps too advanced for a high schooler.

Thomas did not agree with Avicenna that the world is eternal, but he accepted that the fundamental sense of creation is that all existing things depend upon God as cause. Furthermore, he recognized this dependence as ongoing. Creation is not some distant event. If God were not causing all that is to exist, as it exists, there would be absolutely nothing. The expression “creation out-of-nothing” does not mean, first of all, “after nothing.” Rather, it means that in creating God does not use anything; creation is sheer exercise of divine omnipotence.

Thomas clearly saw the difference between the origin and the beginning of the universe. The universe has its origin in God. A temporal beginning concerns the kind of universe God creates. Thomas thought that an eternal universe would still be created. Although Thomas believed the universe had a temporal beginning, he advised against using scientific arguments to prove such a beginning. He always warned against using bad arguments in defence of beliefs.

If he knew contemporary cosmological theories that reject the need for a Creator by seeking to explain the world scientifically or to deny a Big Bang, Thomas would say such an analysis fails on two counts: 1) to deny a beginning is not to deny creation – whatever kind of universe (or multiverse) there is it would still require a cause; 2) speculations about a universe without a beginning (or with a beginning, for that matter) cannot be more than speculations, since, in principle, science cannot know whether there is a beginning. Cosmological theories can neither confirm nor deny creation. To the extent that creation can be grasped by reason, it is through metaphysics, not the natural sciences.