Aristotle’s Substances

This post continues a series on the uses of soul throughout history. The concept plays out very differently in the Bible and Plato, both of which are very different from modern concepts. Today, I’d like to talk about the work Aristotle does with souls, but first I have to say a few things about Aristotle’s worldview in general because he uses souls in concert with other ideas to explain life within a bigger explanation of the world at large.


Aristotle wanted to know about change. What stays the same and what changes? Why do we say that Sharon eats the cookie instead of saying that the cookie dissolves into Sharon? You can speak philosophically and say that Sharon’s essence persists, while the cookie’s essence goes away. Alternatively you can say we care about Sharon throughout, but we care about the cookie before, but only the calories after (the fat and the sugar). It’s no longer useful keep track of the molecules and call them “the cookie.”

Aristotle calls the things we follow substances. Every substance for him has both matter and form. The matter in the cookie is flour, butter, sugar, egg proteins, and (with luck) chocolate. The form is the cookie shape, but also the role of the cookie as a snack. There are many ways we could put the ingredients together and very few of them make cookies. It is important for Aristotle that the ingredients can exist in another form, perhaps cake, and the form can exist in a different way, perhaps a recipe, but a cookie only happens when they come together.

More importantly, neither form nor matter exists alone. The matter of flour may be found in a cookie, a cake, a clump, a pile, or any number of other forms, but it always has a form. (In the Middle Ages, scholars will introduce the concept of formless or prime matter, but Aristotle never speaks of it.) The form of cookie may be present in flour, sugar, etc., for this cookie, in ink on paper for the recipe, or as chemical signals in the brain of the chef, but again, it always has some matter associated with it. (Aristotle gets bit fuzzy about the intellect; maybe it exists apart from matter, but we’ll save that for later.)

Remember this is language for talking about change. Aristotle doesn’t care about which parts are real or even really the cookie so much as he wants words to differentiate what we’re following and what we are not. We follow the substance (form and matter), which stays the same. We don’t follow the accidents, like temperature, size, and taste. So we can say that baking makes the cookie hotter, bigger, and chewier. Only the rare physical chemist follows the heat from oven to cookie, or keeps track of one particular cubic millimeter to see when cookie replaces air in it. No one asks where the chewiness was before it was found in the cookie, or after.

We care about changes in the cookie, at least until it meets Sharon. Then we care about her and say that the cookie ceases to exist. The form of cookie-ness has been separated from the matter.

Aristotle gave us words for understanding why and when we change the subject.

In biology we can get confused about the subject. Individual plants, animals, even people can be difficult to distinguish from their environment. You can eat a carrot. How come the carrot’s molecules become your molecules and not the other way around? What about yogurt? Think about it.

And, of course there will be much more difficult questions. If children are not just parts of their parents, what are they and when do they start to be their own thing? When do we stop caring about and for people within particular bodies? When does a person cease to be a thing, or rather, when do we cease to associate that thing with particular molecules?

It matters when you change the subject.

In the next post, I will talk about Aristotle’s analysis of how change happens and then we will dive into souls as his way of understanding biology.

[Note 1: Aristotle would have said that flour was already a mixture of the matter (the elements earth, water, air, and fire) found in the form of ground up seeds. To what extent Aristotle reduced things to the lowest level would be a different discussion entirely.]

[Note 2: The word essence comes from Latin readers trying to capture Aristotle’s Greek phrase for “what it is to be” for a particular thing.]


5 thoughts on “Aristotle’s Substances

  1. Pingback: Aristotle’s Causes | Science, Spirit, and Scripture

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