  We do not know whether Diodorus had his own modal notions in mind when talking about possibility in his criterion, or just some pre-technical, general concept of possibility, or whether he perhaps intended to cover both (Denyer 1981, 39-41; Sedley 1977, 101-2). (The verb used here for being possible, endechesthai differs from the word used for possibility in Diodorus' modal theory, which is dunaton.) If one assumes that he had his own modal notions in view when giving this account (see sect. 4.2 below), his truth-criterion for the conditional stands in the following relation to Philo's: a conditional is Diodorean true now if and only if it is Philonian true at all times. Diodorus has, as it were, quantified the Philonian criterion over time. The conditional ‘If I walk, I move’ is now true because at no time is the antecedent true and the consequent false. Thus for Diodorus, a conditional cannot change its truth-value. If it is true (false) at one time, it is true (false) at all times. If on the other hand one assumes that Diodorus had some unspecified general notion of possibility in mind when producing his account, the criterion will be correspondingly less specific. However, it would presumably still be a minimal requirement that it is never the case that the antecedent is true and the consequent false.