Chapter 16

36 They say, however, that there is a difference between something without which an effect cannot be produced, and something with which an effect must be produced. None of those things, then, is a cause, since none by its own force produces the thing of which it is called the cause. A cause is not that without which something does not happen, but that which, when it is present, necessarily produces the thing of which it is the cause. Before Philoctetes had been wounded by the snake’s bite, what cause was contained in the nature of things that would bring about his being abandoned on the island of Lemnos? Afterwards, however, there was a cause closer and more directly linked to the outcome.

37 The course of the event, then, reveals the cause. Yet the proposition “Philoctetes will be abandoned on the island” had been true from all eternity, and could not change from true to false. For of two contradictory propositions—and here I call contradictory those of which one affirms something and the other denies it—of these, I say, one must be true and the other false, despite Epicurus. Thus “Philoctetes will be wounded” was true through all the preceding ages, and “He will not be wounded” was false. Unless, perhaps, we wish to follow the view of the Epicureans, who say that such propositions are neither true nor false; or, when they are ashamed of that, still say something more shameless: that disjunctions of contradictories are true, but neither of the propositions they contain is true.

38 What astonishing license, what pitiable ignorance of reasoning! For if something stated is neither true nor false, it is certainly not true. But how can what is not true fail to be false? Or how can what is not false fail to be true? ⟨Therefore⟩ the position defended by Chrysippus will stand: every proposition is either true or false. Reason itself will compel the admission both that some things have been true from all eternity and that they are not bound to eternal causes, but are free from the necessity of fate.

36 They draw a distinction between a circumstance without which something cannot happen and one whose presence makes the result unavoidable. On that account, none of the things mentioned is a cause. None produces, by its own power, what it is said to cause. Something's being indispensable does not make it a cause. A cause must necessarily bring about its effect when it comes into play. Before Philoctetes received the snakebite wound, what cause existed in nature for his being left on Lemnos? After the bite, a cause did exist, closer to the outcome and more directly connected with it.

37 So understanding the outcome shows us what caused it. Still, the statement “Philoctetes will be left behind on the island” was always true. It could not change from a truth into a falsehood. Consider a pair of opposites. Here I mean statements in which one says yes to something and the other says no. Despite Epicurus' objections, there must be a true statement on one side and a false one on the other. Throughout all past ages, for instance, it was true to say “Philoctetes will suffer a wound.” Saying “He will suffer no wound” was false. Unless, of course, we choose to follow the Epicureans! They say that statements of this kind have no truth or falsity. Or, embarrassed by that position, they take an even more shameless one. In their view, an either-or statement made from a contradictory pair is true, but neither of the statements forming that pair is true.

38 What extraordinary freedom to say anything! What a sorry failure to understand argument! Suppose someone says something that has no truth or falsity. At least it is not true. But how can something not true avoid being false? And how can something not false avoid being true? ⟨So⟩ Chrysippus' claim stands: every statement has one of two values, true or false. Reason itself will force this conclusion on us: some things have always been true, yet they have no chain of eternal causes binding them. Fate places no necessity on them.