Rea has argued in “Presentism and Fatalism” that presentism + bivalence + libertarian free will form an inconsistent triad. (The paper can be found here.)
I’m trying to understand his argument. I’ll explain what I take to be the basic strategy behind the argument and why I don’t see how that strategy can succeed. I’ll then offer a hypothesis as to why Rea might have mistakenly thought his argument succeeds. All of this is designed to help you, the audience, understand the nature of my lack of understanding of Rea’s argument. The hope is that someone will straighten me out. (I hope this note isn’t too far removed from philosophy of religion… Rea’s argument does have implications for theological systems: e.g., a presentist might view it as a challenge to the free will defense.)
Suppose for reductio that (i) Sally freely stands up, (ii) presentism is true, and (iii) bivalence is true.
Let P be the proposition that Sally stands up.
Given (i), it seems that Sally has (had or will have) a choice about the truth of P.
Rea’s argument is supposed to reveal that Sally does not have (never had and will never have) a choice about the truth of P if (ii) and (iii) are true. As I understand his argument, his overall strategy is to identify a proposition Q, such that if (i) and (ii) are true, then
(A) There was a time when Sally didn’t have a choice about the truth of Q,
(B) Q entails P.
Rea seems to think that (A) + (B) + plausible auxiliary premises entail that Sally does not have (never had and will never have) a choice about the truth of P.
For the sake of argument, I will grant that if there is a Q that satisfies (A) and (B), then Sally never freely stands up. What I do not see is what Q might be.
After reading Rea’s argument, I thought that perhaps Q is what Rea calls, ‘M2’, which I take to be the proposition that the proposition that Sally will stand in exactly 1,000 years hence was true at a time that obtained exactly 1,000 years ago.
M2 does seem to entail P. So, condition (B) is met. What about (A)? Was there a time when Sally didn’t have a choice about the truth of M2? Not obviously. Notice that M2 is true when and only when P is true: when P is false, it is not the case that 1,000 years ago it was true that in 1,000 years Sally will stand. So there are no times in the distant past, say, when M2 was true but Sally was not around to ground it’s true. M2 is only true when Sally is around and indeed is standing. Thus, I see no reason (in anything Rea says) to think that when Sally chooses the truth of P she doesn’t also choose the truth of M2.
But if M2 doesn’t play the role of Q, what does? I’m at a loss.
Diagnosing the Problem
I have a conjecture as to where Rea’s argument might go wrong. I begin by noticing that instead of P, Rea considers P*, the proposition that Sally stands now, where I’ll assume that P* is equivalent to the proposition that the present time, t, includes (entails) P. Now let M2* = the proposition that there is a time 1,000 years earlier than t which includes the proposition that P will be true in 1,000 years (maybe this is what Rea actually meant by M2). Interestingly, M2* satisfies conditions (A) and (B), with respect to P*: M2* entails P*, and since M2* was always true (including times before Sally was born), there were times when Sally didn’t have a choice about the truth of M2*. The conclusion, then, is that Sally does not have (never had and never will) a choice about the truth of P*. My conjecture is that that conclusion was in Rae’s mind when he concluded that Sally has no choice about the truth of P.
Confusing P* with P would be natural to do from an eternalist perspective, given that truths are typically time-indexed on eternalism (to avoid contradictions: e.g. there are dinosaurs and there are no dinosaurs are both true, but at different times). But if P is not a time-indexed proposition, then P and P* are very different. P* is a necessary truth: it is necessary that P is included in that maximal state of affairs, called t (recall, Rea is supposing the presentist framework according to which times are abstract, maximal states of affairs). By contrast, P is contingent. P was false before Sally was born, for example. P*, on the other hand, was true long before Sally was born. So, just because Sally doesn’t have a choice about the truth of P*, it does not follow that Sally doesn’t have a choice about the truth of P.
Well, that’s just a conjecture about where the argument goes wrong. To be honest, I don’t understand Rea’s argument: I don’t know what he means by various expressions in his premises (such that the premises are plausible and the argument valid). What I do understand is that even if presentism and bivalence are true, neither M2 nor M2*, nor any other proposition I know of, satisfies (A) and (B) with respect to the proposition that Sally stands. Thus, it’s presently not clear to me why combining presentism with bivalence should pose a problem for libertarian free will.
What am I missing?