 In commenting on the notion of contingency in Aristotle’s Prior Analytics, Alexander introduces the idea of stochastic technê — an idea important for the Stoic explanation of virtue that we have just seen. Aristotle himself recognizes a kind of knowledge that deals with things that happen for the most part; what happens for the most part is distinct from what may or may not happen (Prior Analytics, 32b5–20). In his commentary on the kind of syllogism relative to what happens for the most part, Alexander calls the technai that use this kind of syllogism stochastic. The root sense of ‘stochastic’ is the ability to aim or hit. Obviously there is an ambiguity in the notion. A necessary condition of being able reliably to hit the target is being able to aim; but aiming and hitting are different. If one aims well, she usually hits, but contingencies can intervene. Stochastic technai are ones subject to this kind of contingency. Alexander calls them stochastic, in the sense of conjectural (In An.Pr. 39, 15–40, 5). When the physician, e.g., aims at health, his aiming is a kind of conjecture, albeit a grounded one, that such and such treatment will produce health.