The example with which Aristotle introduces problems of inevitability and necessity in Bk. ix of De Interpretatione. It is necessary that either there will be a sea-battle tomorrow, or there will not. Whichever happens, it is now true that it is going to happen, and it has always been true that it is going to happen. So its happening is inevitable, a fact that has existed for all time. It seems as though pure logic implies some kind of predetermination or fatalism. One possible response is to grade future contingent propositions like this as neither true nor false (see many-valued logic). But a less drastic measure is to distinguish between ‘it is now true that a sea-battle will happen’ and ‘the sea-battle's happening is already fixed’, and one test of a theory of truth will be whether it manages to make such a distinction. The problem is sometimes known as the problem of future contingents.