Malcolm Pollack writes,
I hope you'll forgive me for hammering you with emails, but I just wanted to thank you for inviting me to join you in giving this paper a careful going-over. [Christian Wuetrich, "The Fate of Presentism in Modern Physics" in New Papers on the Present, Philosophia Verlag, 2013, 91-131. ] It has given me, as a civilian, yet another opportunity to appreciate the care and attention to detail that professionals in your field must bring to their work. I was struck in particular by this paragraph, from section 3:
"The acceptance of a conflict between presentism and not only SR [Special Relativity], but all of current, as well as prospective, fundamental physics paired with an insistence on presentism amounts to a rather comprehensive rejection of physics. It thus fundamentally contravenes naturalism, a venerable tradition going back at least to Aristotle. According to naturalism, philosophical—and metaphysical—inquiry is continuous with scientific inquiry. To be sure, naturalism is not a logical truth—it is a substantive philosophical thesis. But it is one whose defence has to wait for another day; for present purposes, I simply assume a minimal naturalism which demands that no philosophical thesis be in manifest contradiction to facts established by our best science. Restricting this weak thesis to metaphysics, it can be translated as necessitating that the physically possible worlds are a subset of the metaphysically possible ones, for if the metaphysical theories were in contradiction to the physical ones, then there would have to be some physically possible worlds (and perhaps all) which are metaphysically impossible, as for the metaphysical theory to be incompatible with physics, it would have to rule out some physically possible worlds as impossible. In other words, metaphysics would a priori deem impossible what physics affirms is possible. Assuming that all physically possible worlds are also logically possible, I see little justification for disavowing this weak form of naturalism."
I find this precision, clarity, and style delightful entirely on its own, quite apart from any conclusions it may be leading to. Much obliged.
Malcolm,
I thank you in return for giving me the opportunity to achieve clarity on these topics in connection with a book on metaphilosophy I must finish before the Grim Reaper (Benign Releaser?) lops my head off. As a chess player you know what it is like to be in time trouble with Sudden Death looming, except that it this case it is a scythe and not a flag that will fall. And what the fall will end won't be a mere game.
I will begin by listing some of the main points in W's article, clarifying the key terms, and formulating some of the issues that arise. Ask any questions or make any objections that occur to you. If you find anything I say less than clear, say so. Double quotes mean that I am literally quoting the author. For all other purposes I use single 'quotes.' (One of those uses is instanced in the immediately preceding sentence.) Numbers in parentheses are page references.
1) The author is committed to thinking of time as spacetime, a four-dimensional manifold M composed of "points." (92) These are spacetime points or temporal locations specifiable by x, y, z, and t coordinates, where a spacetime point is a punctuate (duration-less) instant. I take it that M is a continuum so that, between any two instants, or temporal locations, there are continuum-many (2-to-the-alepth-null) instants or temporal locations. This assumes Cantorian set theory and the actual (as opposed to potential) infinite. But then on the same page, he speaks of "events." As I see it, an event is not the same as the time(s) at which it occurs. (The occupant of a spatiotemporal location is not the same as the location it occupies.) I should think that there are times when nothing happens, i.e., when no event occurs, but that whenever an event occurs it must occur at a time or over times. The same goes for spacetime points. Some are unoccupied by physical events, no? An event that is not punctuate like an instant I call a process, even it it lasts only a nanosecond. Nanoseconds and related terms pertain to the "metric" which applies to M. (92) An example of a process, i.e., an extended event, is a storm or a melody. A side point worth pondering is that the universe, supposing it began to exist with a Big Bang, could be metrically finite (12 or so billion years old) despite M's having the cardinality of the continuum, which implies that there are continuum-many events/times between now and the Big Bang
One of the issues that arises here, one not discussed by W., is whether concrete things such as the piano on which the melody is played can be "assayed" (technical term of Gustav Bergmann with mining provenience) as extended events or processes. If so, then pianos and piano players have temporal parts in addition to spatial parts — a view vehemently denied by many philosophers. A melody is not wholly present at every time at which it exists; is the same true of Billy Joel? Melodies and storms unfold over time; they have phases. Do persons unfold over time? Is a person a diachronic collection of person-phases? A person persists through time, no doubt — 'persists' is a datanic term in my lexicon — but does he persist by enduring or by perduring? Is a person or a concrete thing/substance wholly present at every time at which it exists or not? This question goes to the back burner.
2) Given the fundamental presupposition that time is in reality spacetime, eternalism and presentism are defined by the author as follows. Eternalism is "the position claiming physical existence for all events in M," whereas presentism "partitions events into past, present, and future events" together with the proviso that only the events belonging to the present partition enjoy ontological privilege. (92) "Thus the sum total of physical existence is a proper subset of that according to the eternalist." (92)
This I find less than clear. What does the author mean by physical existence? As opposed to what? Surely not mental or abstract/ideal existence. Does he mean the existence of events at times, as opposed to the times at which they exist? An event is not the same as the spacetime point or points at which it occurs. Is it not obvious that the occupant of a location, whether spatial or temporal or spatiotemporal, is not the same as the location? A location exists just as well occupied as unoccupied. Does the author mean to tell us that events exist physically but that times, though they exist, do not exist physically?
Connected with this lack of clarity is the following objection. Presentism is usually explained as the view that temporally present items (whether times or events or members of other categories) alone exist, and thus that wholly past items and wholly future items do not exist, where 'wholly' rules out overlap with the present. If that is what is meant by presentism, then W. hasn't captured it in his definition. For if present items are a proper subset of all existing items (spatiotemporal locations and events at those locations) then those past and future items also exist. But then we are no longer talking about presentism. Presentism is precisely the denial of the existence of the past and the future. The author appear to be begging the question in favor of eternalism by assuming that eternalism is true and that presentism can be defined in terms of it. This ignores the fact that eternalism and presentism are mutually exclusive.
If presentism is the logical contradictory of eternalism, then what exists according to presentism cannot be a proper subset of what exists according to eternalism. The author my be fudging the issue with his obscure talk of physical existence.
3) We were told that presentism partitions M into past, present, and future events. Now what makes present events present? Here is where simultaneity comes into the picture. Simultaneity is an equivalence relation (reflexive, symmetrical, transitive) that effects the partition that creates a proper subset of events, the present ones, and distinguishes them from those to their past and those to their future. This puzzles me for a couple of reasons which I will sketch now, and try to explain more clearly tomorrow.
First, the present as we experience it is not punctuate but specious, in William James's sense of 'specious.' It has a certain spread or duration. 'Now' in 'The sun is now rising' picks out a short period of time that had not yet begun when the sun was below the horizon and will be over a short time later, say in an hour. Sunrise is not an instantaneous event by a a process.
Second, how does what the author says distinguish the present present from past and future presents? After all, at every time or temporal location t in M there is an equivalence class of simultaneous events at t. It follows that there are many — continuum-many! — presents, each equally present at itself. The present present, however, is not merely present at itself, but present simpliciter. It is the 'privileged present,' the absolute present. Presentism is committed to an absolute present. So again, it seems that our author has not put his finger on what privileges the present present, and distinguishes it from past and future presents.