Cahn on Ockhamist Semantics

By 'Ockhamist semantics' ('Ockhamism' for short) I mean the thesis that what's true at a time about other times depends entirely on what occurs at those other times. Thus, if a coin is flipped at T and lands heads at T*, then Ockhamism implies that "The coin will land heads at T*" was true at T, even if (suppose the coin is heavily biased toward landing tails) it was very improbable at T that the coin would land heads at T*.

I think Ockhamism is false, but a lot of philosophers accept it. When asked to give an argument for Ockhamism, they have a standard response. Suppose a person makes a bet that the Red Sox will win the next World Series, and suppose that when the next World Series comes around and the final out is called, the Red Sox are indeed the champions. Wouldn't it be appropriate to say to the person who made the bet, asks the Ockhamist, "Gee, you were right when you said that the Red Sox were going to win"?

Now, this isn't a compelling argument. That we often talk as if something is or was the case doesn't come close to proving that it is or was the case, or even that we believe that it is or was the case. For example, we often speak of the sun's rising and setting, but no educated person today would take that at face value. Still, I'll grant that the Ockhamist's argument has a force. The anti-Ockhamist does have a legitimate burden to explain away our practice of retrospectively attributioning truth (or seeming to do so). But I'm going to set that aside. I've recently begun rereading Stephen Cahn's classic Fate, Logic, and Time (Ridgeview Publishing, 1967) and noticed, in a footnote (p. 36), a retort to the Ockhamist argument:

Consider a man who bets that horse A will win a particular race. After the race is over and horse B has won, the man who bet on horse A is told that at the time he placed his bet it was true that horse B would win the race. Would not the man immediately suspect that the race was fixed? The winner of a bet is the man whose prediction becomes true, not the man whose prediction was true. (my emphasis)

This strikes me as exactly right. If, as of the time the bet was placed, horses A and B were neither guaranteed to win nor guaranteed to lose, then nothing that exists as of that time suffices to make it true that horse B will win the race. So why think it was true then that horse B would win? And if we do suppose that it was true then, doesn't this commit us to there having then been a truthmaker sufficient to make it true then that horse B will win? And if that's the case, then how could we still regard horse B's winning as having been a future contingent rather than as something antecedently "fixed"? A proposition is true at a time if and only if it would be true simpliciter were that time present. But as of the time the bet was placed, nothing that obtained simpliciter sufficed to make it true simpliciter that "Horse B will win" was true then. Hence, "Horse B will win" was not true then, or so it seems clear to me. What we should say, as Cahn suggests, is that "Horse B wins" became true when horse B won. It wasn't true previously.