Book 5
1
False means: (i) false as a thing ; (a) because it is not or cannot be substantiated; such are the statements that the diagonal of a square is commensurable, or that you are sitting. Of these one is false always, and the other sometimes; it is in these senses that these things are not facts.
2
(b) Such things as really exist, but whose nature it is to seem either such as they are not, or like things which are unreal; e.g. chiaroscuro and dreams. For these are really something, but not that of which they create the impression. Things, then, are called false in these senses: either because they themselves are unreal, or because the impression derived from them is that of something unreal.
3
(2.) A false statement is the statement of what is not, in so far as the statement is false. Hence every definition is untrue of anything other than that of which it is true; e.g., the definition of a circle is untrue of a triangle. Now in one sense there is only one definition of each thing, namely that of its essence; but in another sense there are many definitions,Here Aristotle is using the word λόγος not in the strict sense of definition but in the looser sense of a statement about something. since the thing itself, and the thing itself qualified (e.g. Socrates and cultured Socrates) are in a sense the same.
