The Teleological Argument from St Thomas Aquinas - The Fifth Way

Consider a can of flammable liquid. It has a "flammable" label on it because it has a disposition to catch fire or explode, in a way it doesn't have a disposition to freeze or turn into an oak tree. Even if it never catches fire, it still always has that disposition, and thus, in a sense, "points" to the production of fire over ice or oak trees.

Does that sound plausible to you? If so, then you may be skirting dangerously close to final causes/teleology and an argument for the existence of God called the "teleological argument", also known as "Aquinas's Fifth Way."

Let's take a look:

The fifth way is taken from the governance of the world. We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. 

In other words: causal dispositions. Flammable liquid lacks intelligence, but has a disposition to act for the final effect of "flame" and not for the final effect of "ice" or "oak trees".

Now whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer.  

In other words, how does the flammable liquid "know" to act for the final effect of flame rather than ice? We can explain why a person acts for a particular end, because they are intelligent. We can explain how non-intelligent building materials such as concrete and steel act for the final effect of becoming a building because it is directed to that final effect by intelligent beings.

So how can a non-intelligent natural substance act for a specific final effect, since it isn't intelligent? Obviously, because it is being directed by an intelligence, in the same way the builder directs the concrete and steel to become a building.

Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.

In other words, the very existence of causal dispositions shows that there is an intelligence behind the workings of the universe. We could put this argument into a syllogism:

1. Final causes, in order to be efficacious, must exist (duh)
2. If they exist, they must exist either in A) reality, or B) a mind, or C) a Platonic "third realm" (where else?)
3. They do not exist in reality (because they have not happened yet; the flammable liquid has not yet caught fire yet)
4. They do not exist in a Platonic "third realm" (assuming Platonism is false)
5. Therefore, they must exist in a mind

But clearly, no human mind directs flammable liquids to their final effect of flame, so it must be whatever is responsible for the very existence of flammable liquids.

Now consider further that a "disposition" is a potential to act a certain way, but for that disposition to become real, some other state of affairs must "bring it out". E.g., a match must be dropped into the flammable liquid in order to make its potential to be on fire into an actuality, And thus, you also have the beginning of the First Way...