The Categories is an essential text in Aristotle’s body of work.[1] This text seems to be prior to and a foundation for Aristotle’s Metaphysics. The Categories does not deal with why “primary substances” are “substances,” but it does define “primary substance” and “secondary substance,” which appear undefined and unexplained in material form in Metaphysics. A takeaway may be that one should start with Categories before approaching Metaphysics.[2]
One of the interesting features of Aristotle’s philosophy is how grammar seems to model reality. Aristotle’s categorization of things into “primary substance,” “secondary substance,” and “accidents”[3] occurs almost as the result of analyzing the grammatical relationship of the subjects of sentences to the predicates of sentences. This is unclear, and Aristotle does not offer an explanation. If we were to speculate, we might wonder if Aristotle assumed that human reason via human language was in sync with the structure of reality. This makes sense from a Christian perspective since reason would be considered “Logos,” and language would be regarded as “the word,” while Logos created and organized the universe. The Logos connect the universe and reason; language reflects reality for Aristotle like mathematics does for modern science.
Since Categories is about subjects and predicates, we should consider what those terms mean. A subject is the sentence's subject, essentially a noun, a person, place, or thing, e.g., “Peter” or “This bird.” A predicate is what happens to the subject or what the subject does, e.g., “Peter kicked the dog” or “This bird has wings. To get a better sense of what “subject” means for Aristotle, we have to read Metaphysics where we learn that subject is a unitary singular thing. “Two dogs” are not a “subject” in this sense[4]; neither is “pile of sand.”
In Categories, Aristotle observes that subjects can be coordinated with predicates in two primary ways:
1. The predicate can be said of the subject, e.g., “Peter is human” or “Peter is alive.”
2. The predicate can be in the subject, e.g., “Peter is a lawyer” or “Peter knows how to type.” The “in the subject” criteria pertains to things “incapable of existence apart from the said subject.” [Peter’s head can be a subject if separated from Peter’s body, and, maybe, grammatically and less violently as part of Peter while still attached.]
In “Aristotle: A Guide for the Perplexed,” John Vella explains the distinction as follows:
“Being a lawyer” is “passing the bar exam.” Peter has passed the bar exam, but he is not “passing the bar exam.” Thus, “being a lawyer” is something we can say OF Peter, but it is not IN Peter. Similarly, a mammal is warm-blooded and a member of species capable of producing milk. Peter is warm-blooded and a member of a species capable of producing milk. So, “Peter is a mammal” can be said OF Peter, but cannot be IN Peter, since “mammal” is a word for a group and not an individual. (“Mammal” is also not an “accidental” feature of Peter; it is part OF the definition of Peter.)
Put these together, and we have the following scheme:
This may be less than overwhelming, but it is incredibly insightful when it comes to Metaphysics[5] because it identifies a way of thinking about “accidents” and “subjects.” The “subject” falls into the “double No” category because a subject is not in itself (It is itself), nor is the subject said of the subject. A subject cannot be predicated of anything, according to Aristotle. This seems to make sense — how would we make “Peter” a predicate of some other subject?
Aristotle then moves into a discussion of the categories themselves. Categories are those things that are in a subject in the sense that they cannot exist without the subject but cannot be said of the subject. In my chart, this group — Category (III) is what Aristotle calls “accidents.” Accidents are things that can be changed without changing the essence or substance of the subject. If we say, “Peter is a lawyer,” we are speaking about something that cannot be separated from Peter and made to exist separately. Peter’s quality/status as a lawyer lives in Peter; it cannot be carved out and displayed separately from Peter. The classic example is ”Socrates is white.” Socrates’ whiteness is something that cannot be separated from Socrates. “Whiteness” cannot exist as a free-floating thing separated from the thing it makes white.
However, the definition of these things cannot be predicated directly of the subject. I can’t do a better job of explaining this than John Vella does in Aristotle: a Guide for the Perplexed:
Aristotle offers a list of ten categories — one is “substance” (Group (I)), and the other nine fall into Group (III). The nine are:
Aristotle discusses Quality, Quantity, and Relation quite extensively. He gives a summary treatment of the other categories because they are self-explanatory. The one category that may not be for moderns is “affection.” I think “affection” is contrary to “action.” Subjects take actions to impose effects on other things. Subjects are subjected to the actions of others by which they are “affected.” “Affection” means the things to which subjects are “passive recipients.” The Latin word for this is “Passions.” Aristotle explains:
Aristotle then discusses how things can be said to be opposite. There are four ways of opposition. They are:
1. Correlative, e.g., Father/Son; Double/Half.
2. Contraries, e.g., Good/Bad; Health/Disease; Black/White.
3. Privation, e.g, Sighted/Blind.
4. Affirmation/Negations, e.g., “Socrates is ill”/”Socrates is well.”
Correlatives have reference to each other; we can’t have a son without a father. Privations reference a common subject ordinarily existing in the subject, such as the quality of sight. Privation of sight is blindness. Privations may have intermediates. Contraries are not interdependent and may have intermediate states. Affirmations and Negations are qualities of statements and have the quality of “truth,” unlike the other opposites.
As with other features of the Categories, these distinctions are useful for thinking. Categorizing things correctly into proper oppositions allows for more fruitful thinking.
Aristotle’s discussion of movement is like this. Aristotle lists six sorts of movement, four of which are paired. They are:
Aristotle is wonderfully diagrammable. The felicity of this quality is that his key points are more easily memorized. It also provides a structure that permits a fruitfulness of thought. We all know these different aspects of movement but have never structured how we think about motion.
Aristotle is not a light read. His philosophy has much to offer for making one’s way. It is a way of unraveling puzzles that we can find ourselves in. It has much to offer those interested in philosophy or understanding the world. However, I don’t think anyone reading the Categories would get much out of it. Categories should be read as part of a project of learning Aristotle, preferably with the help of other readers. I read Categories and Metaphysics as part of Online Great Books, which provides a reading schedule and a monthly digital seminar to discuss the reading. If you are interested in Aristotle, think about doing it that way.
[1] But what isn’t? Maybe Aristotle’s “Meteorology”? Even obscure entries like “The Heavens” get mentioned frequently in subsequent philosophical works, such as St. Thomas Aquinas’s Summa Theologica.
[2] Also, Categories is shorter and more accessible than Metaphysics. At least, I think so, but that may be because I struggled through Metaphysics before reading Categories.
[3] The Categories does not use “accident,” a word in Metaphysics. Instead, the category of accidents in Metaphysics is the category of “Categories” in Categories, not to be redundant.
[4] Perhaps the clue is in the plural verb (“are”)?
[5] Subjects are indisputable real things. When we say, “The cat is running,” we might wonder about the ontological state of “running,” but that cat
is real.
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