DE&E: Chapter 1:3

Thomas continues to explain the term essence:

Since that through which a thing is constituted in its proper genus or species is what is signified by the definition indicating what the thing is, philosophers introduced the term quiddity to mean the same as the term essence; and this is the same thing that the Philosopher frequently terms what it is to be a thing, that is, that through which something has being as a particular kind of thing.

A definition of thing signifies something less than the fullness of the thing. I can give you a definition of this apple, and the definition will tell you what an apple is, and that this is an apple; but it won’t tell you the exact pattern of red and yellow on the apple’s surface, or whether it is bruised. The essence of the apple is what the definition of an apple signifies, while the color pattern and the bruises are accidents.

Now, the definition of a thing is the answer to the question “What is it?”, or, in Latin, “Quid est?” Hence, the essence of a thing is also called its “whatness,” or “quiddity.”

Essence is also called form, for the certitude of every thing is signified through its form, as Avicenna says in his Metaphysicae I, cap. 6.

Though I believe Thomas makes a distinction between essence and form a little further on. An apple is a composite of form and matter, and it is part of its essence to be so. Therefore, essence cannot simply be form when dealing with material objects.

The same thing is also called nature, taking nature in the first of the four senses that Boethius distinguishes in his book De Persona et Duabus Naturis cap. 1 (PL 64, 1341B), in the sense, in other words, that nature is what we call everything that can in any way be captured by the intellect, for a thing is not intelligible except through its definition and essence.

So, in at least one sense, nature=essence=quiddity.

And so the Philosopher says in V Metaphysicae cap. 4 (1014b36) that every substance is a nature. But the term nature used in this way seems to signify the essence of a thing as it is ordered to the proper operation of the thing, for no thing is without its proper operation. The term quiddity, surely, is taken from the fact that this is what is signified by the definition. But the same thing is called essence because the being has existence through it and in it.

But nature and essence and quiddity, though they all refer to the same thing, do so for different reasons.

I’m curious about the statement I bolded. “…no thing is without its proper operation.” Clearly, “operation” is being used in a different sense than I’m used to. I think I understand what it means, though. A thing behaves in accordance with its nature–at least, things are supposed to. The higher the thing, the more likely it is to behave in an unnatural way. Stones always act like stones. Rabid animals, and animals maddened by hunger, ill-treatment, or injury, can act very differently from normal animals. Men and women, being afflicted by sin, frequently act in ways that are not in accord with human nature–to the extent that we often think that self-destructive and wicked acts are part of human nature.

So I presume that a thing’s “proper operation” is simply “the way it is supposed to behave”.

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