Per se Accidents in Aristotleʼs Posterior Analytics

Abstract

Per se Accidents play an important role in the theory of demonstration. Because if the theory of demonstration has no room to treat per se accidents, then demonstrations will involve no propositions other than definitions, so that all conclusions of demonstrations could be only definitional. Accordingly, Aristotleʼs theory of demonstration would be narrowly limited, if it could not use per se accidents. Aristotle says that the conclusions of demonstration can include per se accidents in APst. A7.
But it is obscure why per se accidents are said to be “per se”. Many scholars have thought that per se accidents use the second sense of “per se” (per se 2） which is introduced in APst. A4. “Per se 2” means that A belongs to B per se when A belongs to B and B is implied in the definition of A. And a per se 2 proposition is a necessary premise. Since Aristotle permits a per se accident as the conclusion of demonstration, per se 2 is not the sense required in per se accidents.
Moreover, in his Metaphysics, Aristotle gives “having two right angles (2R)” as an illistration of per se accidents. On the other hand, Aristotle illustrates “universal” with the example “having two right angles (2R) ”. 2R belongs to a triangle per se and qua triangle, but not in the “per se 2”sense, because triangle is not implied in the definition of 2R.
Consequently we must conclude that Aristotle implicitly admits a new “per se”which includes per se 2 and universal. By using the expression “qua” as “per se” in the broader sense, Aristotle means that per se accidents are proper to a genus as a subject of science, but he does not make this explicit.