Aquinas' Five Ways

Thomas Aquinas proposed five arguments for God in the thirteenth century, and modern Christians still hold them up as good. He did not claim they are proofs, though they are often called that (eg here). Indeed, they could be seen as arguments for the nature of God. We know God exists, but what can we say about him?

They are somewhat obscure, perhaps reflecting medieval philosophy, and people do argue about exactly what they are. I have to qualify this post by saying that this is my understanding of them. I resever the right to update this page if I learn otherwise.

Argument from motion

The first is the argument from motion, by which Aquinas means change. 

• All change happens for a reason,  and that reason is itself a change. 
• Therefore there is either an ultimate "unmoved mover" or an infinite regress of changes.

One problem is that not all change has a reason. Things do happen spontaneously; we know this from quantum mechanics, Atoms of radioactive elements do just decay - there is no trigger. The Second Law of Thermodynamics is based on the hypothesis that energy moves around at random.

None of this was known to Aquinas, so his position is understandable, but when modern Christians use this argument, they are just being ignorant.

However, there are further issues. There is no reason to suppose a single prime mover; there could be many. Further, there is no reason to suppose the prime mover has to be the Christian God, or indeed an intelligent agency at all. Aquinas may well be assuming it is God, and his argument is that "unmoved mover"  is a quality of God.

Is an infinite regress impossible? Or, conversely, is it possible for an unmoved mover to suddenly initiate a move after an eternity of not doing so? I do not find either to be intuitive, but that is the nature of infinity; intuition is not much help.

Argument from cause

This is very similar, but is about things coming into existence.

• Everything that exists does so because of some prior thing. 
• Therefore there is either an ultimate "first cause" or an infinite regress of causes.

This is basically saying every effect has a cause except the first cause, and that is God.

The same response applies here as before.

Argument from contingency

There is some dispute over the meaning; this is my best guess.

• Things have a finite life; they are created and then destroyed; they are contingent
• If everything in contingent then nothing would exist
• Therefore there must be something that is necessary, as opposed to contingent

Again, this looks like Aquinas is arguing about the nature of God, rather than for the existence of God, if only because there is precious little difference between this and the previous two.

Argument from degree

This seems pretty weak to me...

• In any group of things there is one that has the most of a certain quantity (the tallest person in a crowd, for example)
• Therefore, when considering everything, there is one thing that is more good than all else, one that is more just, merciful, etc
• All goodness, etc. must therefore come from that one thing
• That one thing must be God

Why suppose the most merciful thing is also the most just? They seem to be contradictory, for one thing.

Why suppose all goodness comes from the most good? This may be related to Platonic idealism; Aquinas was keen on Greek philosophy. If so, then any Christian using these argument should also hold to Platonic idealism, and I very much doubt that is the case, Can we really suppose that all mass comes from the heaviest object in the universe? That all redness comes from the reddest object? Of course not; this is just nonsense,

Another way of looking at it is:

• Things have varying degrees of how close they are to perfection
• There must therefore be some perfect ideal

I find this no more convincing. Think for a moment about your perfect boyfriend or girlfriend... According to this argument, that ideal is what God is like. Think about the perfect goal or the perfect meal or the perfect day out. That is, according to this argument, God.

Really?

It is sometimes expressed as a standard, that is, the reddest thing is measured against a standard that is the most red can ever be. However, we know from measuring distance and mass that it is more convenient to use a standard that is relatively small, such as a metre or kilogram.

Argument from final end

This is saying (as I understand it) that the laws of nature must have a law maker.

• Things act in a certain way towards a specific end (acorns grow into trees, rivers flow to the ocean)
• There must be an intelligence engineering that to ensure it gets there

I do not believe a rock needs a guiding hand to ensure it falls correctly!

The laws of nature are not like the laws of man; they are of quite a different nature, so there is no need of a law giver. This is, perhaps trivialising Aquinas' argument; he does not quite say that. However, I think the more we learn of the universe the more it seems to be founded on some pretty simple laws.

Schrödinger equation is just four terms, and yet seems to be the basis behind all chemistry, and hence biology. To be sure, the concepts behind the equation require almost a degree in maths to understand, and using it to model, say, two atoms gets very complicated. Plus, it is only a model, and is less accurate in some situations. But it does suggest that behind reality there is a single mathematic equation.

And all the trees, the people, even the apparent laws of nature are merely emergent properties of that.

It is certainly plausible that God created the maths, but it also seems plausible it just happened. And to be honest, I find it more plausible that a single mathematical equation just happened than an unimaginably complex entity like God just happened.

In fact, this is an issue with all these. They are all saying there is some entity behind the universe, some first thing that stops the infinite regress. But none address the issue of why that entity exists.