Academic journal article The Review of Metaphysics

Truth vs. Necessary Truth in Aristotle's Sciences

Academic journal article The Review of Metaphysics

Truth vs. Necessary Truth in Aristotle's Sciences

Article excerpt

AT POSTERIOR ANALYTICS (APO) 1.1.71B15 AND FOLLOWING, Aristotle identifies six characteristics of the first principles from which demonstrative science (apodeiktike episteme) proceeds. These are traditionally grouped into two sets of three: group A: (1) (true) ex alethon, (2) (primary) proton, (3) (immediate) ameson; group B: (4) (better known than) gnorimoteron, (5) (prior to) proteron, and (6) (causes of) [alpha]ition. (1) The characteristic, which I believe has been underrated and somewhat misinterpreted by scholars and commentators from Philoponus to the present day, is the characteristic of truth (alethe). In this paper I propose to present a textually based interpretation of truth that shows the following: (1) that truth is necessarily linked to being (to on). (2) The example given of nonbeing (to me on), the commensurability of the diagonal with the sides of a square, suggests more than simple truth is required for first principles and premises of demonstrative science; and that Aristotle later in the APo changes this characteristic to necessary truth (ex anankes alethes), for he recognizes that truth alone is an insufficient basis for scientific demonstration. (3) The referents of necessary truth are eternal being, and the need for eternal being demands (4) that universals exist extramentally for Aristotle. (5) Finally, one of the important ways that universal genera and species exist for Aristotle are as real, causal principles.

At APo 1.1.71b25-6, Aristotle explains that the principles "must be true (alethe men oun dei einai), because it is hot possible to know non-being (hoti ouk esti to me on epistasthai); for example, that the diagonal is commensurable [with the side of a square]." (2)

While Aristotle seems to be making a rather straightforward claim, that is, that true scientific premises must refer to real being, commentators differ on the meaning and importance of Aristotle's text. For example, Ferejohn claims the following, "To begin with, truth, the first condition listed at 71b6, is no more than an unanalyzable consequence of Aristotle's very minimal requirement that a demonstration must constitute a proof (or sound argument) for its conclusion." (3) It is not clear why Ferejohn fails to mention the example of the commensurable diagonal Aristotle presents in his text, nor is it entirely clear why Ferejohn believes truth is an "unanalyzable" condition. I assume that when Ferejohn speaks of a sound argument, he means its form must be valid and its premises true. I believe Ferejohn has grossly underestimated the importance of truth.

Philoponus presents perhaps the most straightforward account of why Aristotle would claim that the premises of scientific demonstrations must be true. As Philoponus explains, while it is possible to get a true conclusion from false premises, a genuine demonstrative syllogism must have true premises. For example, one could argue that "a man is a stone, a stone is a living animal, therefore, a man is an animal." (4) Although he does not say this explicitly, what Philoponus implies in his example is that a living stone, or a man who is a stone, does not exist and so the premises refer to nonbeing and are false. As Aquinas succinctly summarizes, for Aristotle, "what is not true does not exist, for to be and to be true are convertible. Therefore, anything scientifically known must be true. Consequently, the conclusion of a demonstration which does beget scientific knowing must be true, and a fortiori its premises [must be true]." (5) In the same vein, Byrne notes that "truth, for Aristotle, is correspondence with what is.... [T]he full meanings of syllogistic arguments intend the being of what they state. The whole necessity of the connection between premises and conclusions depends on this.... One cannot have scientific knowledge that a fact cannot be otherwise if there is no such fact." (6)


This last line of Byrne's interpretation implies a problem or limitation of true premises as the bases for necessary conclusions. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed


An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.