Abstract

Aristotle asserts in Met. Theta 4 that „if A, then B“ is a consequence of „if A is possible, then B is possible,“ for any sentences A and B. His assertion has often been questioned, or even been suspected to be a crude mistake. After a discussion of a typical objection, it is shown that a plausible reading of Aristotle’s claim is true: The twice occurring „if – then“ has to be understood in the sense of logical entailment, and sentences suitable as substitutes for the variables „A“ and „B“ are required to contain no modal expressions. The claim in question is the converse of the assertion also advanced in Theta 4 that „if A is possible, then B is also possible“ is a consequence of „if A, then B.“ An application of this cognate of pertaining to the incommensurability of a square’s diagonal is expounded. In the final section, the argument advanced by Aristotle himself in defence of is evaluated