Today we spoke about Thomas Aquinas and the hylomorphic account of nature. Hylo-morphism means “Matter-Form-ism”, and that’s because hylomorphists maintain that a substance is composed of matter plus form. Living things are substances, and they will always be the first examples for philosophers like Aquinas. Thus you are a substance, meaning that you are made of a structure in a physical stuff. Without the structure, you’d be just a heap of parts. Without the physical stuff, there would be no place for you to exist.
The theory of substance is supposed to help account for change. Ancient philosophers were puzzled about how things can change and yet stay the same. Aristotle’s answer - which Thomas Aquinas picked up and defended - was that whenever something changes, something else does stay the same, and the change occurs in that thing. Our first example of this (because remember, we always start with living things) is in animals like us. We change: we grow heavier or lighter, fuller or emptier, more or less tired. These are accidents that occur in the substances that we are, or, if you want to think of substances in the sense that they are the things that remain the same while something changes, in the subjects that are us. For example, when I’m hungry, I am actually unfed but potentially full. Being hungry and being full are two ways in which I can continue to be me.
But what makes Aquinas’ Aristotelian account so powerful is that you can take that same model and apply it to other stuff. Most of the time, any substance you find is made of things that function like substances. I am a form in matter, but my parts (my heart, my eye, etc.) are also forms in matter. It scales. Whatever natural changes you are considering, you look for a subject - the thing that remains the same while other things change. Why do leaves change colour? There’s a substance (the leaf) that is potentially red or yellow, though it may be green now. Artifacts (anything made by human beings that isn’t alive) aren’t true substances, but we can still use the model. My computer is built so that it running MS Word or running Google Chrome are both potential present in it as a subject. And Aquinas theorizes the existence of ‘prime matter’, which is the ultimate subject. If there’s no other matter in play, then a thing would be made of totally formless stuff: prime matter. Of course, we never encounter prime matter in real life, because it would be totally shapeless and unformed.
Because of the power of this theory, Aquinas and others like him thought it could account for pretty much all natural change. In every case of change, there is generation and corruption, meaning just that something that is potentially present comes to be and something that is actually present goes out of being. That’s why John of Salisbury’s investigation of what we would call momentum was so troubling. When you throw an object and it keeps flying through the air, what is the subject that changes and remains the same? It’s not natural to a stone to fly through the air, so that’s not a potential for the stone.
Finally, we took a look at the four Aristotelian/Thomistic causes. As I mentioned, you can think of these as four “becauses”, four answers to a why question that begin with the word ‘because’. Most of the time, we find ourselves talking about efficient causes, but a child often means something else. So a child might ask: “Why are trains the way they are?” You might reply: (1) “Because the train is made of metal and fuelled by an engine, and that’s why it is that way.” In this case, you’re pointing to the matter of the train, which is the material cause. (2) “Because the train is a machine that uses an engine to move people along a track.” That’s the formal cause: the structure of the train is what you are pointing to. (3) “Because an engineer designed it and a factory produced it.” Now you’re talking about what actually made the train happen, which is the efficient cause. (4) “Because people need to get around to other cities.” Now you’re talking about what the train is for: the final cause. Aquinas’ point is that we can always give all four of these “because” replies.