We’re blogging through St. Thomas Aquinas’ Compendium Theologiae, sometimes called his Shorter Summa. Find the previous posts here.
When I first read Chapter 7 of the Compendium, I rather thought that Thomas was repeating himself. In Chapter 3 he showed that God exists; in Chapter 5, he showed that God is eternal. Here in Chapter 7, he’s showing that God exists “always”. Hasn’t he already done that?
I think the key is the distinction between the words eternal and always. As I argued in Chapter 5, to be eternal is to be outside of time altogether: time has no grip on God, who is unchanging. But to be always is to be at every time. God is eternal, outside time, but is also present at every time.
Given that distinction, this chapter is fairly straightforward: Thomas is simply gathering up all of the threads and tying them off in a neat bow. He says,
From all this it is evident that God exists always. For whatever necessarily exists, always exists; it is impossible for a thing that has no possibility of not being, not to be. Hence such a thing is never without existence. But it is necessary for God to be, as has been shown.” Therefore God exists always.
That’s clear: if something can’t not be, then it must be. Thomas showed in Chapter 6 that God is necessary, so it follows not only that He exists, but that there cannot be a time when He didn’t exist.
Again, nothing begins to be or ceases to be except through motion or change. But God is absolutely immutable, as has been proved. Therefore it is impossible for Him ever to have begun to be or to cease to be.
Likewise, if anything that has not always existed begins to be, it needs some cause for its existence. Nothing brings itself forth from potency to act or from non-being to being. But God can have no cause of His being, since He is the first Being; a cause is prior to what is caused. Of necessity, therefore, God must always have existed.
The First Cause cannot come into existence, because by definition there’s nothing to bring it into existence. So given that God exists and is the First Cause, God has always existed.
Furthermore, whatever pertains to anyone in some other way than by reason of an external cause, pertains to him of himself. But existence does not come to God from any external cause, since such a cause would have to be prior to Him. Therefore God has existence of Himself, per se ipsum. But what exists per se exists always and necessarily. Therefore God exists always.
This last bit is a little more complicated. Something that exists can receive its existence from something else; or it can exist by its very nature. Thomas is saying that God exists by His very nature; and consequently exists always. This passage is looking forward to Chapter 11, where Thomas shows that God’s essence simply is His existence: as the Lord told Moses, His name is “I Am”.