Aquinas’s “Five Ways”

We’ll be trying to figure out the structure of Aquinas’s arguments. That is, we’ll be trying to figure out which reasons support which conclusions (conclusions that perhaps are reasons for further conclusions). First, some comments on terminology. The first argument talks about ‘motion’ and a thing ‘moving’ something else. This is a misleading translation since the Latin word really means change in general (e.g., something changing, or ‘moving’ from cold to hot), not just change in position. In the second argument, the expression ‘efficient cause’ is used, but what this means is just what we think of as ‘cause’.

As an example of the structure of an argument, let’s look at his fourth argument (‘way’). The structure of the argument is as follows:

1. There are various things that vary in degree (i.e., that are more or less hot/tall/blue/...).

2. When a thing varies in degree, it varies in this way in virtue of resembling, to a greater or lesser extent, something that has the maximum degree of that quality (e.g., if something is hotter than some other things, it is so because it is more similar to the ultimately hot thing than these other things).

3. That which has the maximum amount of a quality is the cause of all other things resembling it (e.g., that which is ultimately hot is the cause of all other things being hot).

4. Therefore, there must be something that is the cause of all things’ good qualities.

5. Therefore, God exists.

The line drawn under reason #3 shows that #4 follows from the reasons given above it. #5 follows directly only from #4 (though indirectly from all the preceding reasons, since #4 follows from #1 - #3). In other words, #1 - #3 are there simply to support #4, and then this alone is supposed to show that God exists.

Most of us would probably not find Aquinas’s fourth argument very compelling. Look through reasons #1 - #3. Which do you think are true and which not? Look at the very end of his argument, where he says, “and this we call God.” Does this seem like a fair way to argue for his conclusion? Why or why not?

Whenever you read an argument, you should be trying to figure out its structure. So as you read each of Aquinas’s five arguments, you should be trying to understand which reasons support which conclusions, just as was done above for his fourth argument. We’ll focus especially on Aquinas’s second argument, so try to sketch out the structure of the argument. Here are some questions that might help: Why, according to Aquinas, can’t something cause itself? Why can’t the chain of causes go back infinitely far? Why must there be a first cause? And, of course, why should we think God exists?