What better topic of meditation for New Year's Morn than the 'passage' of time. May the Reaper grant us all another year! "I still live, I still think: I still have to live, for I still have to think." (Nietzsche)
If presentism is to be a defensible thesis, a 'presentable' one if you will, then it must avoid both the Scylla of tautology and the Charybdis of absurdity. Having survived these hazards, it must not perish of unclarity or inexpressibility.
1. Only what exists exists.
If 'exists' is used in the same way in both occurrences, then (1) is a miserable tautology and not possibly a bone of contention as between presentists and anti-presentists. Note that (1) is a tautology whether 'exists' is present-tensed in both occurrences or temporally unqualified (untensed) in both. To have a substantive thesis, the presentist must distinguish the present-tensed use of 'exist' from some other use and say something along the lines of
P. Only what exists (present tense) exists simpliciter.
This implies that what no longer exists does not exist simpliciter, and that what will exist does not exist simpliciter. It is trivial to say that what no longer exists does not presently exist, but this is not what the presentist is saying: he is is saying that what no longer exists does not exist period (full stop, simpliciter, at all, sans phrase, absolutely, pure and simple, etc.) He is saying that what no longer exists is nothing.
But the presentist must also, in his formulation of his thesis, avoid giving aid and comfort to the absurdity that could be called 'solipsism of the present moment.' (I borrow the phrase from Bertrand Russell, Human Knowledge: Its Scope and Limits, Simon and Schuster 1948, p. 181.) To wit,
SPM. Only what exists (present tense) exists simpliciter; nothing existed and nothing will exist.
The idea behind (SPM) is decidedly counterintuitive but cannot be ruled out by logic alone. To illustrate, consider James Dean who died on September 30th, 1955. Presentist and anti-presentist agree that Dean existed and no longer exists. (Alter the example to Dean's car if you hold to the immortality of the soul.) That is, both presentist and anti-presentist maintain that there actually was this actor, that he was not a mere possibility or a fictional being. The presentist, however, thinks that Dean does not exist at all (does not exist simpliciter) while the anti-presentist maintains that Dean does exist simpliciter, but in the past. In contrast to both,the present-moment solipsist holds that Dean never existed and for this reason does not exist at all. Thus there are three positions on past individuals. The presentist says that they do not exist at all or simpliciter. The anti-presentist says that they do exist simpliciter. The PM-solispist says that they never existed.
Clearly, the presentist must navigate between the Scylla of tautology and the Charybdis of present-moment solipsism. So what is the presentist saying? He seems to be operating with a metaphysical picture according to which there is a Dynamic Now which is the source and locus of a ceaseless annihilation and creation: some things are ever passing out of being and other things are ever coming into being. He is not saying that all that is in being is all there ever was in being or all there ever will be in being. That is the lunatic thesis of the present-moment solipsist.
The presentist can be characterized as an annihilationist-creationist in the following sense. He is annihilationist about the past, creationist about the future. He maintains that an item that becomes past does not lose merely the merely temporal property of presentness, but loses both presentness and existence. And an item that becomes present does not gain merely the merely temporal property of presentness, but gains both presentness and existence. Becoming past is a passing away, an annihilation, and becoming present is a coming into being, a creation out of nothing.
To many, the presentist picture seem intuitively correct, though I would not go so far as Alan Rhoda who, quoting John Bigelow, maintains that presentism is "arguably the commonsense position." I would suggest that common sense, assuming we can agree on some non-tendentious characterization of same, takes no position on arcane metaphysical disputes such as this one. (This is a fascinating metaphilosophical topic that cannot be addressed now. How does the man in the street think about time? Answer: he doesn't think about it, although he is quite adept at telling time, getting to work on time, and using correctly the tenses of his mother tongue.)
So far, so good. But there is still, to me at least, something deeply puzzling about the presentist thesis. Consider the following two tensed sentences about the actor James Dean. 'Dean does not exist.' 'Dean did exist.' Both tensed sentences are unproblematically true, assuming that death is annihilation. (We can avoid this assumption by changing the example to Dean's silver Porsche.) Because both sentences are plainly true, recording as they do Moorean facts, they are plainly logically consistent.
The presentist, however, maintains that what did exist, but no longer exists, does not exist at all. That is the annihilationist half of his characteristic thesis. It is not obviously true in the way the data sentences are obviously true. Indeed, it is not clear, to me at least, what exactly the presentist thesis MEANS. (Evaluation of a proposition as either true or false presupposes a grasp of its sense or meaning.) When the presentist says, in the present using a present-tensed sentence, that
1. Dean does not presently exist at all
he does not intend this to hold only at the present moment, else (1) would collapse into the trivially true, present-tensed, Moorean, 'Dean does not exist.' He intends something more, namely:
2. Dean does not presently exist at any time, past, present, or future.
Now what bothers me is the apparent present reference in (2) to past and future times. How can a present-tensed sentence be used to refer to the past? That's one problem. A second is that (2) implies
3. It is presently the case that there are past times at which Dean does not exist.
But (3) is inconsistent with the presentist thesis according to which (abstract objects aside) only the present time and items at the present time exist.
My underlying question is whether presentism has the resources to express its own thesis. Does it make it between the Scylla of tautology and the Charybdis of PM-solipsism only to founder on the reef of inexpressibility? Just what is the presentist trying to say, and can it be said?
I have long held that time is the hardest of all philosophical nuts to crack. I fear it is above my pay grade, and yours too.
Happy New Year!