Philosophy

5

LECTURE: Aristotle’s philosophy of nature

We’re building up to a look at the view about the soul and its relationship to the body developed by the ancient philosopher Aristotle (384 - 322 B.C.) and his medieval follower Thomas Aquinas (c. 1225 - 1274). Properly to understand it, though, we need to see how Aristotle and Aquinas conceived of the natural world in general. And as I noted last time, that, in turn, can only be understood against the background of the Pre-Socratic philosophers Aristotle was reacting against. Let’s look now at how he does that.

Act and potency

The foundation of Aristotle’s view about how nature works is the distinction he draws between act and potency – or, to use somewhat more modern language, actuality and potentiality. The basic idea, once you understand it, is actually very simple. And yet, in Aristotle’s view, the key mistake thinkers like Heraclitus, Parmenides, and Zeno make is to overlook it.

Here’s how it goes. Consider any ordinary object, such as a red plastic ball of the sort a child might bounce around. In order to have a full description and understanding of it, one of the things we need to know are the different ways in which it is actual: it is actually round, actually red, actually solid, actually sitting motionless in a drawer, and so on.

But in addition to that, for a full description and understanding of it, we also need to know its potentialities: it is potentially moving (if you throw it), potentially green or blue (if you paint it), potentially flat and squishy (if you melt it), and so on. These are real features of the ball, no less than its being round, red, solid, etc. are. After all, not everything is potentially true of it. For example, it has no potentiality to grow legs and follow you around or to grow teeth and bite you. But, again, it does have the potential to become a different color, or to melt, or to move. So, again, these potentials are in a sense really in the ball itself, no less than the ways in which it is actual are in it. Actualities and potentialities together make up the full reality of the thing.

You’ve got a lot of potential, kid

Now, actualities are more fundamental than potentialities, in a couple of ways. First of all, a thing’s potentials are grounded or rooted in the ways it is actual. For example, a plastic ball has the potential to be melted in a microwave oven because it is actually made of plastic. Had it been made of something else instead (such as stone or steel) it would have had a much higher melting point, and would not have the potential to melt in a microwave.

Because potentialities are rooted in actualities, Aristotle thinks that there cannot be anything that is purely potential, or in no way actual. If there were no actualities to ground its potentialities, it just wouldn’t exist. However, there could be (and indeed, he thinks there is) something that is purely actual, with no potentiality. In fact, that is the core of Aristotle’s idea of God as what he calls the “Prime Unmoved Mover” of the world. We’ll come back to that later on. The point for the moment is that Aristotle holds both (a) that actuality and potentiality are crucially different aspects of a thing, though also (b) actuality is more fundamental than potentiality.

Change is the actualization of potential

Well, so what, you may ask? Isn’t the distinction between actual and potential pretty obvious? Why is it important? One reason it is important is that it is the key to seeing where Heraclitus, Parmenides, and Zeno all go wrong. Start with Parmenides. Recall that he argued that change is impossible, because (he claimed) it involves being coming from non-being, or something coming from nothing. Since that is impossible, change is impossible.

Aristotle agrees that being cannot arise from non-being. But he holds that that is not what change involves. Instead, change involves the actualization of a potential, and a potential is not nothing, it is not a kind of non-being. For example, when a plastic ball is melted in a microwave oven, the potential squishiness of the ball is actualized. The squishiness doesn’t go from non-being to being or from nothing to something. Rather, it goes from potential to actual.

What Parmenides overlooks, in Aristotle’s view, is that potentiality is a middle ground kind of reality between actuality on the one hand, and non-being or nothingness on the other. Parmenides draws the following distinction:

Being

Non-being

Parmenides then concludes that if something does not exist (as the squishiness of the ball does not exist before the ball is melted) then it must be a kind of non-being or nothingness. But that’s too simple. The distinction Parmenides overlooks is this:

Being-in-actuality

Being

Being-in-potentiality

Non-being

Again, change isn’t a matter of going from non-being to being, but rather involves going from one kind of being (being-in-potentiality) to another kind of being (being-in-actuality). Once we make that distinction, Parmenides’ argument against the reality of change collapses.

Dance off, bro! Parmenides vs. Aristotle

Zeno overlooks the distinction between actuality and potentiality as well. Recall the dichotomy paradox, in which it is claimed that a runner can’t get from point A to point B because there are an infinite number of ever-smaller distances in between. And no one can get across an infinite number of distances. Aristotle would say that Zeno’s mistake is in thinking that the shorter distances are there actually. In fact they are there only potentially. In actuality there is only the finite distance between A and B to get across, not an actually infinitely large collection of smaller distances.

A similar mistake occurs in Zeno’s paradox of parts. Recall that Zeno says that if there really were different objects in the world, they would be infinitely divisible and have an infinite number of parts – in which case they’d be infinitely big. Aristotle’s response is that these parts are indeed in a thing, but only potentially rather than actually. Until you actually divide a thing, the parts are not actually present. So, it doesn’t follow that a thing is made up of an actually infinite number of parts, and we don’t have the absurd result that it is infinitely big.

Finally, there is Heraclitus, who makes a different mistake. Heraclitus, you’ll remember, thinks that there is no stability in the world, nothing that persists over time even for a moment. There is only pure flux or endless change. He is, in effect, describing a world of pure potentiality, which never succeeds in actualizing into anything. But, again, Aristotle would say that there can’t be such a world, since potentiality must be rooted in actuality.

Form and matter

The distinction between actuality and potentiality is completely general, applying to everything except what is pure actuality (which, again, we’ll come back to later). Hence, suppose there are immaterial or non-physical things, such as disembodied souls. (Whether there are or not is irrelevant for the present point. It’s just an example.) They would still have to go from potential to actual.

When we come to the world of physical objects, specifically, though – rocks and trees, dogs and cats – actuality and potentiality come to us as form and matter. The form of a thing is the pattern or organizational structure that makes it the distinctive thing that it is. The matter of a thing is the stuff out of which it is made, that which takes on the form.

Form and matter are clearly different aspects of a thing. The same form can exist in different bits of matter; for example, the same form or pattern of being a triangle can exist in this set of ink marks and that one, this set of pencil marks and that one, and so forth. And the same matter can take on different forms. For example, the same ink can be in a liquid state when in a pen, then take on the form of a triangle when you draw a triangle on a marker board, then take on the form of dust particles when you erase it. But it is only form and matter together that give you an actual physical object. There is no such thing as the form of a triangle floating around by itself, apart from matter; and there is no such thing as ink not having some form or other, whether it is a liquid form, a dried out form, or whatever. (Note from this example that a form doesn’t have to be a shape. It could be any pattern – a color, solidity, dryness, whatever.)

Now, form is to matter as actuality is to potentiality. Matter by itself has the potential to take on different forms; form is what actualizes that potential so that the matter becomes some specific kind of object (a triangle, a table, or whatever). The form/matter distinction is essentially what you get when you apply the actuality/potentiality distinction to physical things, specifically. It’s a more specific kind of actuality/potentiality.

Hylomorphism

Aristotelian philosophers like Aquinas draw some further distinctions. Where form is concerned, we can distinguish between a substantial form and an accidental form. A substantial form is what gives a substance the distinctive nature that it has, its characteristic properties and ways of acting. For example, we might say that to have the substantial form of a fish is to fit the pattern of being a cold-blooded vertebrate animal with gills and fins and living in water. Having that form is what makes a fish the kind of substance that it is.

An accidental form, by contrast, merely modifies in some non-essential way a substance that already has a substantial form. For example, for a fish to be green or blue or silver is for it to have a merely accidental form. A fish would still be a fish whatever color it had; but it would not still be a fish it if was not a cold-blooded vertebrate animal with gills and fins and living in water. So, being green or blue or silver is a merely accidental form of a fish (where “accidental” here means something like “non-essential”).

It was accidental, honest!

Where matter is concerned, we can distinguish between prime matter and secondary matter. Secondary matter is matter already having some form or other. All the physical objects we actually come across are like that. Prime matter would be matter having no form at all; it would be nothing but the pure potentiality to take on form. Now, because potentiality can never exist without actuality, prime matter can never exist on its own. In reality outside the mind, matter always has some form or other – it is always secondary matter. But at least in thought, we can separate out the form of a thing and consider its matter in isolation, and arrive thereby at the idea of prime matter.

Now, these concepts give us what we need to give a precise definition of Aristotle’s view about what it is to be a physical object. It’s called:

hylomorphism: the view that all natural substances are composites of prime matter and substantial form, related to one another as potentiality and actuality

The word “hylomorphism” comes from the Greek words for matter and form (so that the word means something like “matter-form-ism”). As we will see, for Aristotle and Aquinas, this is crucial to understanding the relationship between body and soul. They hold that the soul is the substantial form of a living body. But what that means, why they believe it, and what its implications are are topics we will come back to.

The four causes

Aristotle held that when we ask for the cause of a thing, there are really four different things we have in mind, or should have in mind – four essential aspects of a complete explanation of a thing. They are:

1. Material cause : This is just the same thing as the matter out of which a thing is made, which we’ve already talked about. For example, think of the plastic out of which the ball in our example is made, or the muscle tissue out of which a heart is made.

2. Formal cause : This is the same thing as the form or pattern that a thing’s matter has taken on, resulting in a thing of a certain type. We’ve already talked about this too. Think of the spherical and solid structure that the plastic has, which makes it a ball. Or think of the organization of the muscle tissue of the heart into ventricles, atria, etc.

3. Efficient cause : This is what brings a thing into existence or changes it in some way. It’s what we usually think of these days when we hear the word “cause.” Think of a worker making the ball in a toy factory by pouring molten plastic into a mold, or the process of cell division that generates the heart.

4. Final cause : This is the end, goal, or purpose for the sake of which a thing exists or acts. For example, the final cause of a ball is to function as a toy, and the final cause of the heart is to pump blood.

Four causes

Final cause

In the Aristotelian tradition, the final cause is considered especially important – Aquinas calls it “the cause of causes.” There are a couple of reasons for this. For one thing, the rest of the four causes depend crucially on the final cause. Consider another example, a hammer. It’s because it has the final cause of pounding nails that it has to have a certain formal cause, namely a certain shape and solidity. That, in turn, requires a certain material cause, because not every kind of matter can take on that sort of shape and solidity. And that entails, finally, a certain kind of efficient cause, since not everything can bring a hammer into existence. The final cause is thus what ultimately determines all these others.

A second point is that there is a crucial link between final cause and efficient cause. For we find in our experience of the world that efficient causes reliably and predictably bring about certain kinds of effect. For example, if you plant an acorn, you’ll always get an oak growing out of the ground (as opposed to a dog, or a Volkswagen, or what have you). If you strike a match, you will reliably get flame and heat (as opposed to ice, or a nuclear explosion, or some other weird effect).

Of course, if you damage an efficient cause in a certain way (e.g. you get the match wet or crush the acorn), you will not get the effect. But the point is that if an efficient cause is undamaged and operating under normal conditions, it will always produce the same effect. Why is this?

Aquinas’s answer is that the only way to make sense of why some efficient cause A reliably produces a specific effect or range of effects B (rather than C, or D, or no effect at all) is that generating B is the final cause of A – it is the end or goal that A naturally points to or aims at. Usually this is not conscious. A human being or other animal can be consciously aware of the ends or goals it aims at, but an acorn is not! All the same, in an unconscious way, there is in the view of Aristotelians like Aquinas a kind of “aiming” or “directedness” toward an end state in every efficient cause. (That things naturally aim at or are directed toward end states is also called their “teleology” – a word that derives from the Greek word telos , which means “end” or “goal.”)

Actuality and potentiality, form and matter, four causes, teleology… This might all seem very dry and abstract, but next we will see how Aristotle and Aquinas start to draw some dramatic and surprising conclusions from this general picture of how nature works.

Here are some optional YouTube videos exploring some of these ideas:

Aquinas 101 on Act and Potency:

https://www.youtube.com/watch?v=7AzrbXjDLiM

Aquinas 101 on Form and Matter:

https://www.youtube.com/watch?v=rGXMo28Bqsw

Aquinas 101 on the Four Causes:

https://www.youtube.com/watch?v=QDVON6DeZaM