Consider the following from Aristotles Categories:

Substance, in the truest, primary and most definite sense of the word, is that which is neither predicable of a subject nor present in a subject.

We have however, the sentence

Socrates is Socrates

Socrates, as the individual man, I take it is a subject; I also take that the sentence is true; supposing this sentence is a predication, then we can't take Socrates as a substance; if it's not, then we can.

But it's implied in other places that individual things are substances of a kind, so one should take the above sentence is not a predication.

But, given that this is a true sentence, should we distinguish this kind of sentence from predication; say, by calling it a tautology, or identity - does Aristotle, himself, do so?

Is this kind of sentence normatively distinguished from predication; or taken to be a special kind of predication?


Substance has a long history, but here I'm concerned what Aristotle means by substance in the Categories, or in his own works - since he occasionally refers to it elsewhere.

  • Are you asking if a sentence can be "true" without predication? Or are you asking if a tautology is a predication? Or are you asking if an individual human being is a substance? Something seems mixed up here. Commented Dec 12, 2015 at 4:09
  • @alexander: I' trying to work out what's being said in the categories; going on what I know how predication is used in set-theory, I'd say that identity is a kind of predication; but going on how A is implying what it is meant by predication, then identity isn't - presumably because nothing is being said of the subject. Commented Dec 12, 2015 at 4:22
  • I'm not even sure that Aristotle uses the term tautology; I just threw it in coming from a modern logic perspective. Commented Dec 12, 2015 at 4:26

1 Answer 1


Some initial suggestions :

and :

  • Simo Knuuttila & Jaakko Hintikka (editors), THE LOGIC OF BEING : Historical Studies (1986), at least : BENSON MATES, Identity and Predication in Plato, page 29-on, and JAAKKO HINTIKKA, The Varieties of Being in Aristotle, page 81-on.

For Arsitotle's theory of substance and predication, see Aristotle's Categories :

given the above interpretation of the said-of and present-in relation, a primary substance is a particular that is non-accidental.

Thus, according to this interpretation, Socrates (the individual) is a substance.

Aristotle's categorialism is firmly anti-Platonic. Whereas Plato treated the abstract as more real than material particulars, in the Categories Aristotle takes material particulars as ontological bedrock — to the extent that being a primary substance makes something more real than anything else, entities such as Socrates and a horse are the most real entities in Aristotle's worldview [emphasis added].

Due to the Platonic background of many of A's thesis, see Mates' study, page 29 :

In recent times this situation has been analyzed on the basis of the assumption that the verb "to be" has at least two senses, viz., the predicative sense, as in "Socrates is human", and the identity sense, as in "Socrates is the husband of Xanthippe". Plato's critics castigate him for being unaware of the distinction, while his defenders believe that he was perfectly well aware of it and that the allegedly self-predicative statements are to be understood as assertions of identity.

And see Hintikka :

Almost all twentieth-century philosophers in English-speaking countries have followed Frege and Russell and claimed that the words for being in natural languages - "is", "ist", etc. - are ambiguous between the is of predication, the is of existence, the is of identity, and the generic is.

For Aristotle discussion of "sameness", see Topics, Book I: 103a32, and see Beck [page 182] :

So he admits self-predication, in the sense of having the expressions contained in the subject and the predicate signify the same item in a category. [...] Aristotle says that in cases of sameness in number we uses two appellations of the same thing.

and Beck, [page 184] :

The aspect theory can handle identity claims: 'Socrates is Socrates' becomes 'Socrates exists as (identical to) Socrates'; 'this man is Socrates' becomes 'this man exists as (the same as) Socrates'. Such statements are harmless but not too informative. We can see why Aristotle would not think that the identity relation has central importance in predication. [...] Aristotle allows predication at best only of expressions signifying singulars in accidental categories (taken abstractly). He does not seem to allow the predication of singulars in the category of substance. Still his remarks on numerical sameness to offer a way of analyzing such singular statements as 'the one drinking hemlock is Socrates' without predicating a singular term: not 'is Socrates'; rather take the predicate as either 'the same as Socrates' or, better, 'being Socrates' (sc., 'the essence of Socrates' — suggested by the predicative position).

For A, strictly speaking, a singular term (the name of an individual) cannot be predicated:

Of all the things which exist some are such that they cannot be predicated of anything else truly and universally, e.g. Cleon and Callias, i.e. the individual and sensible, but other things may be predicated of them (for each of these is both man and animal).[An.Pr., Book I, 43a32-3]

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