Truth (Aristotle)

Metaphysics

Possibly Aristotle's most well-known definition of truth is in the Metaphysics, (1011b25): “To say of what is that it is not, or of what is not that it is, is false, while to say of what is that it is, and of what is not that it is not, is true”.

For example, assuming that it is the case that snow is white, and that it is not the case that snow is blue, then we speak falsely if we say that snow is not white, or if we say that it is blue. And we speak truly if we say that snow is white, or if we say that snow is not blue. It is not clear whether he has a so-called correspondence theory of truth in mind, or something more like a deflationary theory, since he is not clear about what aspect of reality is responsible for truth or falsity.

See also Metaphysics Book II 993b30-31 "The principles of eternal things must be always most true (for they are not merely sometimes true, nor is there any cause of their being, but they themselves are the cause of the being of other things), so that as each thing is in respect of being, so is it in respect of truth". However, this creates difficulties for scientific or mathematical statements which seem to be eternally true, yet may have no instances at some point in time – was the proposition 'any triangle has three angles' true before any triangles existed?

In Metaphysics Book VI c. 4 1027 b20 he says that being true or false depends on combination and separation in judgment, then adds puzzlingly that falsity and truth are not in things "it is not as if the good were true, and the bad were in itself false".

Categories

Si solum addatur modus et non res tunc gratia modi causatur distinctio, tunc non causabitur veritas vel falsitas gratia istius modi quia in eo quod res est vel non est etc. The medieval scholastic logicians frequently cited Aristotle's characterisation of truth in Categories 4a35

Something more like a correspondence theory is evident in The Categories.

• Chapter 5, 4a35
  • "Statements and opinions themselves remain unaltered in all respects: it is by the alteration in the facts of the case that the contrary quality comes to be theirs. The statement 'he is sitting' remains unaltered, but it is at one time true, at another false, according to circumstances. What has been said of statements applies also to opinions".
  • "If, then, a man should make this exception and contend that statements and opinions are capable of admitting contrary qualities, his contention is unsound. For statements and opinions are said to have this capacity, not because they themselves undergo modification, but because this modification occurs in the case of something else. The truth or falsity of a statement depends on facts (Eo enim quo res est vel non est, eo oratio vel vera vel falsa dicitur), and not on any power on the part of the statement itself of admitting contrary qualities".
• Chapter 10, 12b5
  • "That which is affirmed or denied is not itself affirmation or denial. By 'affirmation' we mean an affirmative proposition, by 'denial' a negative. Now, those facts which form the matter of the affirmation or denial are not propositions; yet these two are said to be opposed in the same sense as the affirmation and denial, for in this case also the type of antithesis is the same. For as the affirmation is opposed to the denial, as in the two propositions 'he sits', 'he does not sit', so also the fact which constitutes the matter of the proposition in one case is opposed to that in the other, his sitting, that is to say, to his not sitting".

• Chapter 12, 14b15
  • "The fact of the being of a man carries with it the truth of the proposition that he is, and the implication is reciprocal: for if a man is, the proposition wherein we allege that he is true, and conversely, if the proposition wherein we allege that he is true, then he is. The true proposition, however, is in no way the cause of the being of the man, but the fact of the man's being does seem somehow to be the cause of the truth of the proposition, for the truth or falsity of the proposition depends on the fact of the man's being or not being".

De interpretatione

Aristotle's definition of truth in the first chapter of De interpretatione suggests something more like a coherence theory of truth. Truth is a matter of composition or separation.

Chapter 1 "As there are in the mind thoughts which do not involve truth or falsity, and also those which must be either true or false, so it is in speech. For truth and falsity imply combination and separation".

Commenting on this passage, Peter Abelard says that if someone judges that Socrates is a philosopher, they join the idea of 'philosopher' to the idea of 'Socrates'. Or if they think that Socrates is not a philosopher, they separate the idea of 'philosopher' from the idea of 'Socrates'.

Qui enim intelligit Socratem esse philosophum, intellectu suo philosophiam Socrati componit, id est copulat et coniungit. Qui vero intelligit Socratem non esse philosophum, in intellectu suo philosophiam a Socrate separat et dividit, et ita intellectus affirmationis componens, intellectus negationis dividens appellatur [1].

De Anima

In De anima 430b26-30 (not in Logic Museum), he says "Every utterance, e.g. an affirmation, is of something, about some subject; and is always either true or false. Yet not all understanding is thus; understanding is true about what anything is, in the sense of the quiddity of it; not as to every fact about a subject, but, as sight is always true about its proper object, yet it is not always true about a white thing being a man or not. So it stands with whatever is immaterial".