Proposition and Tense

McTaggart assumed (1) that propositions cannot change in truth value and (2) if (a) there is real change, then (b) events must acquire the absolute property of being present and then lose this property. He held that {1,2b} is an inconsistent set and thus inferred ∼2a—that there is no real change. The B theory rejects 2 and the A theory rejects 1. I accept 1, 2, 2a, and consequently, 2b, and argue that this is consistent. There is an absolute property of presentness, but we can never predicate this property without producing an assertion in which that property is “chronologized.” If at t, we attribute presentness, we thereby attribute presentness-att. We can grasp the existence of an absolute property which we are unable to attribute absolutely. Kant discusses a formulation of what he calls “the principle of contradiction”: “It is impossible that anything should be and at the same time not be” [ 1]. He objects that the term “impossible” is redundant, and more importantly, that the principle “as a purely logical principle, must not be limited in its application by time; and the beforementioned formula runs therefore counter to its very nature.” Kant is not saying that the formula is not a necessary truth. Nor is he saying that there are no things such that they could at one time be and at another time not be, so that the formula for such things would require the temporal qualification he finds objectionable in a logical law. It is just that for such things as propositions, as intended in classical logic, we say simply that no such thing can be both true and not true, without needing any such qualification as “at the same time”. Temporally qualifying the principle of contradiction may suggest that it is about things that change truth value over time. Of course, the principle is about absolutely everything, including itself, and including sentences or “propositions” which change truth value over time. But it could be held that the principle does not require temporal qualification even for one who believes that propositions change truth value. It is a defensible view that “Nothing is both red and not red” is not refuted by the existence of a wall which is at one time red and at another, not. Similarly for all properties, whether or not they are “chronologized.” Still, Kant’s point has a stylistic basis. Received September 29, 1998; revised March 1, 2000 PROPOSITION AND TENSE 251 The formulation he criticizes suggests (even though it may not entail) the attitude that propositions, as properly intended in the classical rule that no proposition is both true and false, are of a nature such that we should add the qualifier “at the same time.” We may consider whether this is true. An example of something which might seem capable of being true at one time and false at another is: A. The sundial is illuminated at present. There may be a notion of “proposition” such that some such is associated with the sentence A in certain uses and, like the sentence, changes in truth value. But let us consider the proposition in the classical sense, as the entire content of what is said in aparticular use of A. Suppose someone uses A to make a statement at noon on Monday. At noon on Tuesday he asserts the sentence A again, in reference to the very same sundial, to the very same audience. We can keep the circumstances as similar as we like, except that there is a day separating the two assertions. The proposition conveyed by asserting the sentence A on Monday is MA, the one on Tuesday is TA. Question: Is MA = T ? Someone who holds there is such a property as being present should feel some pressure to conclude that MA = TA. It would seem that both attribute the very same property, being illuminated at present, to the very same thing, the sundial. One could hold that in spite of this, they differ in content. But then it should be a problem to explain how they differ, for those who hold that there is a property of being present and thus a property of being both present and illuminated. Consider the following: B. This case of the sundial’s being illuminated is present. Could this sentence B be used on Monday to make the same assertion as MA? What information would be conveyed by asserting one that would not be conveyed by asserting the other? One suggestion (due to an anonymous referee) is that use of “this case” signals that a direct reference by ostension is being made, and this is information not signaled by the use of A. On this account, the content of MA is conveyed by MA*: The sundial’s illumination has the property of presentness, whereas the content of MB is conveyed by MB*: Whatever case of the sundial’s illumination that is being demonstrated or ostended has the property of presentness. The suggestion is that A could be used to refer to a case of a sundial being illuminated when the dial was not in the near vicinity and not being ostended, for example, if the speaker and audience were in the United States and the dial were in Egypt, while B could not properly be so used. On the contrary, B could just as successfully be used to refer, from the vantage of the U.S., to a dial in Egypt. There would need to be some prior understanding that a sundial in Egypt is under discussion, perhaps concerned with various important consequences triggered by the exposure of that dial to light. Having described the results of a number of cases of illuminating the dial, perhaps by moving it outside or