In chapter 9 of de Interpretatione (henceforth ‘Int. 9’) Aristotle claims that some future-tense singular assertions are sometimes neither true nor false, and therefore refute Bivalence, the principle stating that every assertion is always either true or false. Aristotle's argument goes as follows:

Int. 9 divides into four parts: the first (18a28–33) is introductory (it briefly states Aristotle's position); the second (18a34–18b25) contains two arguments from Bivalence to Determinism; the third (18b26–19a22) argues that Determinism is absurd; the fourth (19a23–19b4) contains Aristotle's solution to the problems raised by Bivalence and Determinism.

In section 1 of the present chapter I present the most important modal attributes and theses at play in Int. 9: the attribute of necessity as ineluctability (a diachronic modality, with two ‘slots for dates’), the thesis of the necessity of the present and the past (the thesis that for whatever obtains at any time it is both then and later necessary to obtain then), and Determinism (the thesis that for whatever obtains at any time it is always antecedently necessary to obtain then). Aristotle endorses the necessity of the present and the past, but rejects Determinism.