Thursday, December 26, 2013

A Simple Formulation of the Fourth Way

The Fourth Way of Thomas Aquinas, known colloquially as the argument from perfection and the argument from gradation has numerous formulations.  One easy way to state the argument is like this:

1. A flaw or degree in something cannot be known unless there is a standard of perfection for it. (Premise)

2. There are flaws in truth-claims and degrees of goodness. (Premise)

3. Therefore, there is some Supreme Truth and Supreme Goodness that is the standard of perfection by which the imperfection of other things can be intelligible. (From 1 and 2)

In support of (1), C.S. Lewis is famous for stating that a man would have no idea what a crooked line looks like unless he already knew what a straight line looks like.  The fact that there is deviation entails that a thing must deviate from some standard of perfection.  Given premise (2), which appears obviously true, it follows that there is some standard of perfection for truth and goodness, which we call God.


  1. I see two problems with the argument.

    First, it seems to me that the standard of perfection could be something solely in the intellect. I have never seen a perfectly straight line. It is the concept of a straight line in my intellect that I compare actual lines against.

    Second, the standard of perfection for different things is different. A perfect line is different from a perfect circle. It is not clear how God is the standard of perfection for geometric shapes or many other things.

  2. Jayman, the standard of perfection could only exist in the intellect if one is willing to bite the bullet and state that truth and goodness are relative. The fact that you have a concept of a straight line in your intellect does not undermine the objectivity of what a straight line looks like independently of your conception of it.

    With respect to your second point, of course standards of perfection are different for different things. A perfectly straight line will be distinct from a perfect circle. That doesn't take anything away from the standard of perfection about truth: it is objectively true that a straight line will not be crooked, and it is objectively true that a perfect circle will have a diameter of approximately 3.1416.

    The reason God is understood as the standard of perfection for both truth and goodness is because that's the very definition of God on classical theism. Whatever is most true is most actual. Since there is a Supreme Truth, it follows that there exists something which is most actual: Pure Actuality, e.g. God.

  3. In case it helps to understand where I'm coming from, I understand the Fourth Way as a kind ontological argument. I'm doubtful that the fact that we can conceive of a standard of perfection in our minds means that the standard exists independently of our minds.

    I don't see why maintaining that the standard of perfection exists in the intellect requires that truth and goodness are relative. Presumably we both have in our minds the same understanding of what a straight line is. It is objective in this sense. Yet this does not require that there is a Platonic form of the perfect line or some material line somewhere that is perfectly straight.

    The fact that different things have different standards of perfection makes it less than evident how the conclusion to the argument (as you've outlined it) is that God exists. Why not conclude that a perfect line exists, for example?

  4. That's an excellent question, and it allows me to clarify my own position on the Fourth Way. I'm a conceptualist, meaning I view abstract objects as existing, but existing as mental concepts. Straight line, perfect circles, as well as perfect truth and goodness are all abstract objects. However, they are necessarily existent abstract objects (or so I maintain). What this means is that these abstract objects exist even if there are no contingently existing minds, which entails the existence of a necessary mind, e.g. God.

    Of course, I would have to present an argument for all of that. Here's a very brief article I wrote in the past: