4.1 Divine Eternity (SCG 1,15)
4.1 Divine Eternity (SCG 1,15)
Also on the basis of SCG 1,13, Aquinas declares in SCG 1,15 that God is eternal. Here, and in line with the “way of remotion,” Aquinas construes “eternal” in negative terms, in terms of God not being something or other. For Aquinas, something eternal does not have a beginning or end and does not have existence that can be measured by time.
Beginning or ceasing to exist, Aquinas argues, depend on motion or change. If God is immutable, however, then God must lack beginning or end. When it comes to eternity as not involving temporality, Aquinas appeals to something that Aristotle says about time in Physics IV. According to Aristotle, we can only “measure” a thing temporally on the basis of changes that it undergoes. We cannot conceive of something having a history if the thing in question is immutable. So there is no “before” and “after” in God, and God must have “his whole being at once” and is, therefore, eternal.3
Could it, however, be that God began to exist having formerly not existed? No, replies Aquinas, since that would mean that God derives from a cause while God is the first cause. “That which has been everlastingly,” says Aquinas, “has the power to be everlastingly.”4 To this argument Aquinas adds another:5
1. The world contains things subject to generation and corruption, things that can equally be or not be.
2. Something that can equally be or not be must have a cause of its being.
3. As we saw in SCG 1,13, there cannot be an infinite series of hierarchical causes.6
4. So there must be at least one necessary being.
5. A necessary being must either have the cause of its necessity from something other than itself or it must have its necessity from itself.
6. “One cannot proceed to infinity among necessary beings the cause of whose necessity lies in an outside source.”7
7. So there is “a first necessary being, which is necessary through itself.”8
In this argument, “necessary” is contrasted with “being generated” and is not equivalent to “being logically necessary” or “having to exist as a matter of logical necessity.” Aquinas is not saying that there has to be something (God) the existence of which it would be self-contradictory to deny. Nor is he saying that there could only be one necessary being. He is saying that something not generated exists and that its existence is either derived from something else or had by nature by the thing in question. Either way, thinks Aquinas, we are led to suppose that there is something that is necessary and owes its being to nothing outside itself. And, says Aquinas, such a being can be thought of as eternal, as the Bible says that God is.