Presentism and Causation

I'm rather attracted to presentism, the view that the present is coextensive with the real. The past is no more; the future is not yet; whatever exists simpliciter exists now.

Presentism is one of several views that affirms an A-theory of time (roughly, the A-theory says that temporal becoming is real, and not merely apparent). One of presentism's advantages over other A-theory variants is that it nicely avoids McTaggart's Paradox. Presentism's main advantage over B-theories of time (roughly, the B-theory says that temporal becoming is merely apparent, not real) is that it squares much more closely with common sense.

But presentism is not without its problems. One apparent difficulty is called the truthmaker objection. Since presentism denies that past facts exist, the presentist needs to find something else to ground truths about the past, and it's by no mean obvious what that could be. I think this difficultly can be answered and have proposed a solution here. The solution trades on the idea that the past leaves causal traces in the present. Given that these traces satisfy certain contraints that I spell out, they can serve as truthmakers for truths about the past.

But this brings us to another difficulty, one that I am just beginning to think about and am not yet sure how to answer. It is expressed rather well by Robin Le Poidevin (a B-theorist) in his book Travels in Four Dimensions:

Consider the statement 'The past leaves causal traces on the present.' What, according to the presentist, makes this statement true? Well, present fact, presumably, since that is the only kind of fact available. But what purely present fact could make true a statement about the causal relations between different times? We can make sense of a past event leaving its causal traces on the present (last night's wild party has left a number of traces around my sitting-room, for instance: the smashed wineglass, the shoe-marks on the piano, the underwear draped over the sofa), but can we make sense of the causal relation between that event and the present traces itself leaving its traces on the present? The idea is a distinctly odd one. Any statement about the relation between different times (or between the events that occurred at those times) requires us to stand, in thought at least, outside those times and view them as of equal status. There cannot be a relation if one of the things the relation is supposed to relate is just not part of reality. It looks, then, as if the presentist is not entitled to assume the only mechanism that can explain, in terms of present fact, how statements about the past can be true. (p. 139)

Here's the problem in a nutshell: To meet the truthmaker problem, the presentist needs to appeal to causal traces left by the past on the present. But this looks to be positing a real causal relation between past events and the present. A real relation, however, obtains only if all of its relata obtain. Hence, past events can be causally related to present events only if past events really exist. But presentism denies that past events exist (only the present is real), so it seems like the presentist cannot answer the truthmaker objection after all.

Is this a decisive objection against presentism? Well, I'm not convinced, for reasons explained below. Anyway, off the top of my head I can think of a few possible lines of response.

1. Deny that causation is a relation, despite appearances to the contrary.
   
2. Deny that all real relations are existence entailing. Ordinary relations imply the existence of their relata but some relations, among them (some) causal relations, don't.
3. Deny that causal relations are relations between events, but rather relations between some other category of thing - perhaps "states of affairs" or "substances".
4. Deny that causal relations are relations between event tokens, but rather relations between event types. Hence, causal relations hold between abstract objects.

These may not be the only options, but none of these looks particularly attractive. 1, 2, and 4 are extremely counter-intuitive. 3 is more plausible, but it runs counter to long-entrenched views in philosophy that analyze causation in terms of events and, furthermore, its not quite clear that shifting categories from events to something else still won't commit the presentist to some kind of past existents.

Perhaps there's a fifth option: Deny that the truthmaker for "the past leaves causal traces on the present" requires positing real causal relations between past and present events. How so? Well, if we think of time like a presentist does, then what is real now (the present) is already pregnant with powers and propensities that will usher forth in a new reality, replacing the old one. Imagine that one of these powers is global in extent, fully reflexive, and at each new moment gives rise to a new state that retains a complete snapshot of the previous moment - kind of like a universal video recorder that, as reflexive, also records its own recording (and records its own recording of its own recording, etc.). If this is coherent, then maybe my proposed solution to the truthmaker objection (linked above) can also be pressed into service here.

I've argued that a presentist ought to be a theist, because the best (if not the only) way to solve the truthmaker objection is to ground truths about the past in God's memories. Given that God exists noncontingently, experiences time, and is omniscient, then God retains a perfect and complete memory of each successive moment of time. As omniscient, God's perspective fully reflexive and transparent such that in knowing P God knows that he knows P and knows that he knows that he knows P, etc., without the addition of any new facts. Hence, the truthmaker for "It was the case that P" is just God's remembering that P, and the truthmaker for "God remembers that P" is again just God's remembering that P. (Note: It is an established principle that one truthmaker can ground multiple truths.)

Is this a solution to Le Poidevin's challenge? I am inclined to think so. It does, however, suggest a way of thinking about causation that may be peculiar, namely, as the exfoliation of internal propensities through the exercise of some kind of 'active power' (to use Thomas Reid's phrase). I'll have to reflect more on that in a succeeding post.