Aquinas Explainer: The Fifth Way

Warning: amateur philosophy ahead!

Aquinas’ Five Ways arguments for the existence of God are usually misunderstood nowadays. It’s not so much that they are complicated; rather, because they are so different from modern Western thought, it takes a little while to wrap your head around them.

Most people assume his argument from design (the Fifth Way) is a god-of-the-gaps argument that has been refuted by evolution. Not only is that not the case, but the argument cannot possibly be refuted by any scientific theory. To find out why, read on.

Imagine if you will, a group of scientists performing an experiment on water. They heat the water but instead of boiling at 100 degrees as expected, it boils at 75 degrees.

What caused this to happen? The scientists may consider the following:

– Something is wrong with their equipment
– There are impurities in the water
– Igor swapped the water with vodka again
– Under a specific set of circumstances previously unknown to science, water boils at 75 degrees

And here are some options the scientists will likely not consider:

– The water is conscious and sabotaging our experiment
– Glitch in The Matrix
– Water changes at random and just doesn’t make sense. Who can understand it?
– Water has stopped working. Guess we can’t drink it any more
– Looks like water is taking Tuesdays off
– Water has changed by decree of the secretive Water Committee. It will now boil at a lower temperature than what it used to

Why don’t the scientists consider the second set of options? It is because the natural world is extremely regular and predictable. If it wasn’t, science would scarcely be possible.

It is this regularity about nature that Aquinas is trying to explain.

Water being water, it has properties such that when it is heated to 100 degrees it boils. In Aquinas’ metaphysics, this means water has an essence that includes being internally “directed to” boil under the circumstance that it is heated to 100 degrees. This is called “intrinsic teleology”. “Teleology” meaning that it points to an end goal, in this case that of boiling at 100 degrees. “Intrinsic” because it is part of its internal nature, rather than being imposed by any outside forces.

Anything science can tell us can be described in this way. All material things, because they are what they are, can be described as having an essence, that is internally “directed to” behave in certain ways, in a predictable fashion that can be studied by science.

That’s all background. While it is part of Aquinas’ metaphysics it is not part of the Fifth Way and stands or falls on its own merits.

The Fifth Way

But why do things have this intrinsic teleology? It didn’t have to be this way. In an alternate universe, perhaps nature would behave in an arbitrary fashion which is not predictable, follows no rules and cannot be studied by science. Since logically nature could have been arbitrary, there must be a reason for why is isn’t.

Aquinas argues that since natural things are “directed to” their ends, and that they predictably meet those ends, this can be compared to arrows that always meet their targets. Arrows that always hit the bulls-eye tell us there is an archer. Likewise, since natural things are always “directed to” their ends, this is by design. But natural things don’t have intelligence, so they can’t be their own designer. “Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.”

Does evolution show that the Fifth Way is wrong? No, because evolution is simply natural things behaving in a predictable way just as Aquinas is describing.

What are the alternative explanations? Some might say that nature “just is” predictable and that there is nothing to explain, but I don’t think this will do. A policeman who discovered a dead body would not assume that it “just is” there with no need to investigate further. You can’t just assume that something requires no further explanation; you have to prove that.

I think the Fifth Way is still a good argument which deserves consideration and is not hard to understand once you understand the background assumptions.

There is a lot more that could be said here, much of it above my pay grade. There are further details, arguments, counter-arguments, counter-counter arguments, counter-counter-counter arguments and so forth, all in copious amounts beyond what any person could reasonably want, for philosophy is a bottomless pit.

For more information on the Fifth Way, this blog post is externally “directed to” provide you with the following links:


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