What is nature, and how is it different from the artificial, according to Aristotle?

An important, timeless question: what distinguishes the natural from the artificial, and what does it mean to be natural, anyway? Aristotle (384 - 322 BC) tackles this big question at the start of the second book of the Physics, which is his work dedicated to the investigation of nature.

This is a question that many people reflect on today: how can we draw the line between natural and artificial? It was especially pressing for Aristotle in the 4th century BC because his own teacher and most important predecessor, Plato (428 - 348 BC), had argued in the Timaeus that the entire universe was the product of a divine craftsman, whom we call the Demiurge. In Plato’s view, everything is an artifact. The whole world is artificial, a product of the god's art and made in accordance with his divine blueprint.

Aristotle strongly disagrees. He thinks that we can and should distinguish between the natural and the artificial.

The difference between them is that the natural has within itself a starting point, or a “principle,” of change and the cessation of change. It has a source of motion and being at rest within itself.

The artificial, meanwhile, has the source of its motions and rest external to it. Its changes come from the outside.

Some examples will help illustrate the distinction, but first, let’s turn to Aristotle’s own words from the Physics:

“Of the beings, some are by nature, while others are due to other causes. Those that are by nature are animals and their parts, plants, and simple bodies - for example, earth, fire, air, and water (for we say that these and things like them are by nature). All these things evidently differ from things that are not composed by nature. For each of them has within itself a starting-point of moving and being at rest-some with respect to place, some with respect to increase and decrease, others with respect to alteration” (Physics II.1 192b6-15).

Here’s what Aristotle is saying: among the things that exist, some are natural, but some are not. The list of natural things includes living things and the four elements. (In fact, Aristotle thinks that there is a fifth element that he doesn’t mention here, but that is irrelevant to the point.) These things are clearly different from artificial things. Why? That’s because they have internal to them a source, a starting point, or a principle (these words are synonyms) of motion and rest. There are different kinds of changes that they could undergo, but the point is that so long as the source of their motion is internal to them, they are natural.

Trees are natural, and they grow without anyone making them grow.

Humans are natural, and we grow without anyone making us grow.

Dogs are natural, and they grow, move, and do all sorts of things without anyone making them.

Could someone force a plant to grow in an unnatural way? For example, maybe I make plant grow upwards and sideways along the wall of my house by shaping a path for it. Absolutely, this is possible. And Aristotle would say: that’s unnatural. Why is it unnatural? Because it was a motion whose source was outside of the plant; after all, it was imposed by me, an external person.

This leads us to Aristotle’s discussion of artificial things:

“A bed, by contrast, or a cloak, or anything else of that kind, insofar as each such predicate applies to it — that is, to the extent that it is a product of craft — has no innate impulse to change” (II.1 192b15-17).

Here’s what he means: when we consider examples of artificial things, which are the products of human crafts and intervention, what we notice is that they have no ability to change on their own.

A bed doesn’t grow into existence like a tree does. Beds need to be brought into existence by some external agent. That’s why they are artificial.

Now, here’s a small complication. All artificial things are made of natural things. For instance, our beds are made from the wood that was once a tree. Aristotle recognizes this, but he doesn’t think it takes away from his point. Sure, artificial things coincidentally happen to be made of natural things, but they lack a source of change and rest that is internal to them. So, they are not natural any longer.

It might be surprising to you that Aristotle thinks that all artificial things are made of natural things. You might think that beds being made of wood are a good example of that, but aren’t there plenty of counter-examples? Is a brick really made of something that was once able to change on its own?

Aristotle says: yes!

In fact, we already saw why. Aristotle thinks that the four elements — earth, air, fire, and water — are natural things. They might not grow in the same way that plants and animals can, but they are natural. They have a source of motion in themselves.

Aristotle is trying to explain why rocks always fall. They always fall because they have a natural tendency to move in that direction. They have a downward motion that is natural to them. Aristotle doesn’t know about gravity, so he creatively explains these motions in terms of nature.

All the elements have a natural direction to their movements, as a matter of fact. Water moves downwards, too, just as earth does. Fire and air move upwards naturally.

Does that mean that, say, earth can’t move upwards? Not at all. We can throw rocks upwards, if we want. That’s subjecting them to an artificial motion — an unnatural motion, in other words— just as making plants grow sideways up the wall of my house is artificial.

So, that’s the major distinction between natural and artificial things: the former have a source of change that is internal to them, whereas the latter do not. When we speak about artificial and natural motions, we can ask similarly whether the motion came from the outside or was internal to thing that is moving.

We can even take a large step back and say: this is what Aristotle thinks that nature is overall. Nature is an internal principle, source, or starting point of change.

Why does this plant grow pine needles at the end of its branches? That’s what is in its nature. This means: it has an internal source of motion, and the motions in question lead to the development of pine needles at the end of its branches. These motions are the ones studied by biologists in their quest to understand plant growth and development.

That doesn’t mean that you can’t chop off the branches altogether, but that would be an artificial change imposed from the outside.

And we could spell out tons of other examples. Human bodies naturally develop teeth and feet, and that’s because our bodies have a nature, too: the transformations in us that lead to the development of these anatomical features aren’t imposed from the outside; they are part of our nature, and their source is internal to us.

This is Aristotle’s impressive, rich, and sophisticated analysis of the distinction between natural and artificial, in the light of which he produces an account of nature as an internal source of change.