June 04, 2014

The 5 Ways of Thomas Aquinas

Stephen Nichols
The 5 Ways of Thomas Aquinas


On this episode, we’re going to be diving right into a heavy-duty thinker, and some heavy-duty topics. We’re going to dive right into philosophy. And our guide for some of this philosophical conversation is going to be the great medieval thinker, Thomas Aquinas.

Now Thomas Aquinas worked on his magnum opus for decades—the Summa Theologica. The best way to translate this would be "The Highest," "The Best of Theology.” One way would even be to translate it, “The Most . . .,” and that might be a fitting description. This is a massive work that just goes on and on for volumes. And in fact is technically unfinished. Aquinas never quite finished it before his death. It’s a work that is full of many ideas, but one of the ideas that comes down to us, and this is both in the history of Christianity and even in the history of philosophy. If you look at philosophy textbooks you would find references to this. And this we call “Thomas’ 5 Ways,” or “The 5 ways that the existence of God can be proven.” Well, let’s see if we can work through these.

The first way he borrows from Aristotle, and Aristotle would speak of an "unmoved mover." See, Aristotle thought that of all of reality, one of the things you could know for certain is that there is motion. And in order for there to be motion there had to be something that started motion. And for an argument that’s a little intense, we probably won’t go into, he said you can’t just simply have motion going into eternity backwards—that is, if you look back in time you can’t have simply motion going all the way back into eternity. Because if that was the case, you’d never start if it went back ad infinatum, as the Latin says, “to infinity.” You’d never start. But we know motion started. Why? Because we have present motion. So, Aristotle posited the idea of an unmoved mover. And Thomas Aquinas comes along and says the unmoved mover is God. Now that’s the first way.

The second way is sort of applying this logic of the unmoved mover, but now Aquinas is going to speak in terms of causes. And so he says one of the things that we can observe in the world is that we see cause and effect in reality. One of the ways you can see this very clearly is if we were to go play a game of pool, or billiards as we might say. And every time of coarse you hit the cue ball, and it hits into another ball, the ball that the cue ball hits, moves. That is what we see as a cause and effect. The effect of the one ball moving is set in play by the cause of the cue ball hitting it. And the cue ball moving is set in play by the pool stick hitting the cue ball. And the cause of the pool stick hitting the cue ball is set into motion by the pool player who pushes the pool stick along. So we see cause and effect. And again, if we apply that logic of "You can’t go back in infinity," you can’t go back ad infinitum or you’d never begin. And so we have the second way which is simply "God is," what Aquinas would call, “the first cause.”

The third way has to do with the nature of being and Aquinas says, “Well, there’re contingent beings, and there are necessary beings.” And so contingent beings are ones who are dependent upon something else for their existence. But for all these beings who are dependent upon something else for their existence, there needs to be something behind them that is independent. So that is a necessary being. And of course, that’s God.

Then we come to our fourth way, and Aquinas says, “Look around and what we see as we observe reality is gradations of being." There are things that are better, and there are things that are worse. In order to have better and worse, well we need two categories. We need “the best” and we need “the worst.” In other words, we need perfection. And so we need a perfect being behind these gradations of being that we see in reality. And again, that perfect being is God.

Well, that leads us to our last. And our last is what Aquinas calls “the argument from design.” You see, all natural things are oriented towards a goal and a purpose. And where does that come about unless they are being guided along by an intelligent being who is a designer? And that intelligent being is God.

And so we have Thomas Aquinas and his 5 ways for arguing the existence of God.