We lost the brilliant E. J. Lowe (1950-2014) at an early age. We best honor a philosopher by thinking his thoughts, sympathetically, but critically. Lowe writes,

When we say that Caesar has ceased to exist, what we really should mean is that he is no longer a part of reality at all, any more than Sherlock Holmes is, in fact, a part of reality . . . . This, of course, raises the question of how we can so much as talk about Caesar now that he no longer exists simpliciter — how we can speak about 'that which is not.' It also raises the question of how we can still distinguish between the ontological status of Caesar and that of Holmes, and resist saying that Caesar has 'become' a fictional object in something like the sense in which Holmes is. But these questions are not, perhaps, so difficult to answer, once we understand aright the metaphysical picture that is being proposed. With regard to the second question, we can still say that Caesar really did exist, unlike Holmes. And with regard to the first, we can say that the proper name 'Julius Caesar' is perfectly meaningful, not because it now has an existing referent, but because its use is historically traceable back to a referent that did exist — pretty much in line with the 'causal' theory of reference advanced by Saul Kripke. ("How Real is Substantial Change?" The Monist, vol. 89, no. 3, 2006, p. 285. Italics in original.)

What no longer exists did exist but does not now exist.  That's just what 'no longer exists' means. But is it true that what no longer exists does not exist at all? Lowe answers in the affirmative.  Of  course, what no longer exists does not exist now, but that is tautologically true and of no metaphysical interest.  Lowe is telling us something of metaphysical interest about time, existence, and their 'relation.' He is telling us that what no longer exists and is wholly past has been annihilated. Not only does a past item not exist now, it simply does not exist: it does not exist simpliciter as we say in the trade. It is no longer a member of the sum total of what exists. When a thing passes away it falls off the cliff of Being into the abyss of Nonbeing.  And so I cannot say, now and with truth, of Jack Kerouac (1922-1969) that he would have been 100 years old this year had he lived. But I just did! I referred to him successfully and I made a true statement about him, that very person. And what were the birthday celebrations in his hometown of Lowell, Massachusetts about if they were not celebrating his birth? However things stand with respect to the future, the past surely seems to have a share in reality.  If the past has no share in reality, what do historians study?  Will you tell me that they study the causal traces in the present of past events? But if the past has no share in reality, if the past is not, then those traces are traces of nothing, and the historian is not an historian but a student of some weird merely present things.  Will you tell me that the past WAS? Well, that's surely true, but not to the point. The question is whether what WAS has a share in reality as opposed to being annihilated, reduced to nothing, by the passage of time. 

In general, what should a Lowian presentist say about past-tensed contingent truths? There are plenty of them, whether we know them or not, and whether or not the things they are about have left any causal traces in the present.  And they are true now. It is the case that Julius Caesar was assassinated.  What makes it true now that Caesar was assassinated?  Surely nothing that now exists makes it true, and if only what exists now exists simpliciter, then nothing makes true contingent past-tensed truths.  Some say that such truths are brute truths: they are just true without anything that explains their being true, or that grounds their being true, or that 'makes' them true. This is a very bad answer as I could easily show; in any case it appears not to be Lowe's answer given his acceptance of truthmakers:

I should also reveal that I am an adherent of the truthmaker principle, according to which all truths — all contingent positive truths — require the existence of a truthmaker; something which, by existing, makes them true. (288, bolding added)

On the face of it, there is a tension, if not a contradiction, in Lowe's position. His presentism commits him to saying that nothing that now exists could serve as the truthmaker of a past-tensed positive (affirmative) truth such as the one expressed by 'Julius Caesar existed.' But if all contingent affirmative truths need truthmakers, as per the quotation, then so does the truth that Julius Caesar existed, in which case Lowe is telling us both that past-tensed truths must have, and cannot have, truthmakers.  That certainly appears to be a contradiction. Is there a way around it? For maximal logical clarity, I cast the puzzle in the mold of an aporetic triad:

a) All contingent affirmative truths need truthmakers.
b) 'Julius Caesar existed' expresses a contingent affirmative truth.
c) 'Julius Caesar existed' cannot have a truthmaker.

This trio is collectively inconsistent: its members cannot all be true. Since (b) records a pre-philosophical datum, it cannot be philosophically denied. (An historian might attempt to show it false, but then I would simply change the example.) So the question boils down to whether we accept the truthmaker principle as explained by Lowe (to which explanation I have no objection)  or accept instead Lowe's (non-ersatzist) presentism. (Lowe rejects ersatzism.) We cannot accept both, as Lowe appears to do.  Thus I smell a logical contradiction.  Or is this an olfactory hallucination on my part? 

Lowe tells us that the proposition that Julius Caesar exists "is now false but was once true." (289) For "it formerly had a truthmaker — namely, Julius Caesar himself — but no longer does." (289)  If a proposition can change its truth value from true to false, then, given the truthmaker principle, the proposition in question had a truthmaker, but has one no longer. Fine, how is this relevant? The question concerns the truthmaker of the proposition that Julius Caesar existed. The question is  not whether the proposition that Caesar exists had a truthmaker.  The question is: what makes it true that Caesar existed is true? What makes it true now that Caesar existed can't be the fact that Caesar exists had a truthmaker but has one no longer.  For what makes it true now that the proposition that Caesar exists had a truthmaker? Nothing at all if presentism is true. 

Lowe maintains that a truthmaker is "something which, by existing, makes them [positive contingent truths] true."  Truthmakers, then, must exist to do their jobs: there are no nonexistent truthmakers. But on presentism only what exists at present exists simpliciter. Wholly past truthmakers do not exist. So it is simply irrelevant to invoke them if the question concerns the truthmakers of presently true past-tensed truths.

As I see it, Lowe cannot  solve what is called the 'grounding problem,' a problem that ineluctably arises for him because of his (laudable) commitment to truthmakers.  The problem, simply put, is that past-tensed contingent affirmative truths (true propositions) need ontological grounds, i.e., truthmakers. He cannot solve the problem because of his creationist-annihilationist version of presentism.

I now turn to the other problem Lowe mentions in the passage quoted above, the problem of  referring to what no longer exists given the presentist view that what no longer exists does not exist at all.   Lowe tells us that "the proper name 'Julius Caesar' is perfectly meaningful, not because it now has an existing referent, but because its use is historically traceable back to a referent that did exist . . . ." Lowe mentions Kripke's causal theory of reference.  It is difficult to see how there could be any historical tracing if all of past history has been annihilated by the passage of time. 

More needs to be said. But brevity is the soul of blog, as some wit once opined.