Ammonius and Chapter 9 of Aristotle's De Interpretatione

The much debated chapter 9 of Aristotle's De interpretatione raises a difficulty regarding the distribution of truth values between the members of a contradictory pair for contingent futuretense singular assertions. This article addresses Ammonius' reading of the issue by analyzing in detail the arguments he presents against determinism. Ammonius' solution mainly consists in introducing a distinction absent from Aristotle's text between dividing true from false in a definite vs an indefinite way. The author clarifies the meaning and implications of such a notion, thus arguing for Ammonius' ascription to the so-called non-standard interpretation of Aristotle's chapter. It is also argued that Ammonius' commentary, though not providing a decisive solution to the problem, is nonetheless coherent and offers an interesting insight. The general aim of the article is, therefore, to contribute to the long-lasting debate on De interpretatione 9 in an indirect way, namely to understand the deeper implications of the famous Aristotelian chapter by delving into one of the solutions offered by the tradition.