If you study theology—maybe not even professionally—you’ve probably noticed that there are plenty of different views with different opinions on various different subjects within theology.

I’ve heard someone say that if you get ten theologians in a room, you’ll have ten different views between them. We’ll, I’d even venture to say that if you get ten theologians in a room, you’ll have 20 different views between them! Because they don’t only disagree with each other; they disagree with themselves!

Now I’m not just picking on theologians here. The sentiment is true among different disciplines of study as well. But what I’m getting at is this slew of criticism toward Aquinas and his followers particularly among the Reformed crowd.

All you need is the Bible—that’s a given—and John Calvin and you’re done. Maybe some Jonathan Edwards for good measure, and if you really want to go far back then throw in Augustine.

But Aquinas really set the groundwork for theology today, and yes, even for—maybe even especially for—Calvin. So what is it that makes Aquinas so darn great?

Easy. His metaphysics. I say that kind of jokingly because if you’re a novice to Thomism then you understand that he’s quite difficult to just pick up and read. If you’re a long time student of Aquinas works then you know he’s difficult to just pick up and read!

One of the keys to understanding Aquinas metaphysics is understanding his doctrine of being. Particularly the distinction between essence and existence. This distinction is Aquinas’ main contribution to philosophy—in my humble opinion—and he did make a lot of contributions. His essence/existence distinction is also what sets him apart from Aristotle.

Before we talk about that it’s important to understand Aquinas on act and potency.

Potency and Act divide being in such a way that whatever is, is either pure act, or of necessity it is composed of potency and act as primary and intrinsic principles.

Taken from the 24 Thomistic Theses.

Stated more clearly, one of the key ideas in Aquinas is the idea of motion, or change. Simply put, things change. To change means to move from potency to act. For example, an acorn is just an acorn, but in it, is the potentiality to become a tree. When an acorn changes from an acorn to a tree it’s potential to become a tree has been actualized. It’s potential has moved from potency to act. Whereas before it was an acorn and only potentially a tree, it is now actually a tree. Potency —> Act.

There is definitely much more to be said on this topic however this blog is not intended to be a full blown academic essay, rather it’s a way to share and hopefully develop an interest in Thomism for the reader. Admittedly this is a very simplified (overly simplified) explanation.

Moving on…

In God, however, there is no potency. God does not possess the potential to change. After all, He is unchanging (Malachi 3:6). More so there is no room for change in God because He is already perfect. There is no room for change, no need for development, God is already perfect. There is no potency in Him, He simply is Actus Purus (Pure Act).

Whatever is composed of act and potency needs a cause to account for this composition; however, God being Pure Act is not composed and therefore has no cause but is the cause of everything else that exists because everything else is composed of act and potency.

If I haven’t lost you yet, the next thing to understand is the distinction between essence and existence. More on that in part 2 titled, “What Sets Thomism Apart?”