Presentism seems to be popular among some Christian philosophers, William Lane Craig being the most prominent. Allow me to defend the “block” view of time that the past and future really exist.
Objection to the idea that the past doesn’t exist
There are purely philosophical considerations that are, I believe, decisive on their own. If the past is not real, there is no ontological ground upon which statements about the past can be true or false. Piety toward ancestors would be meaningless. No one could be responsible for past actions, but only present memories or expectations. A totally forgotten crime really never happened.
Objection to the idea of a “flow” of time
The idea of a “flow” of time is ill-defined, because there is nothing with respect to which time could be said to flow.
Objection to abandoning the doctrine of God’s eternity
Abandoning a four-dimensional view of time means rejecting the doctrine of classical theology that God is atemporal. If God exists in time, His knowledge must include A-series type propositions and thus must be time-dependent, which throws other classical divine attributes into question. It also rules out the Boethian solution to the problem of divine foreknowledge and free will. If God only sees the present but knows the future, determinism must be true. Being a compatibilist, this doesn’t bother me much, but I expect it would bother many of you.
Objection to an ontologically preferred slicing of spacetime
Finally, there is the problem of positing a privileged foliation of spacetime. The issue is not just that presentism must assume the existence of an absolute reference frame of which the laws of physics are ignorant, although that in itself is a strong mark against it. The problem is rejecting the great philosophical insight of special relativity, that the whole idea of an absolute standard of simultaneity across all space was never part of our core intuition of the essence of time; it was always unneeded metaphysical baggage.
The core intuition of time is connected to causality: the past influences the present (i.e. we remember it), and the present influences the future. Relativity preserves this, in that for any two events all frames will agree on whether or not one event is in the other’s past light cone. If two events cannot influence each other, common sense should tell us that they share no temporal relationship, and indeed they don’t. Different frames will disagree about which of two spacelike-separated events happen first, but our real sense of time is time along a single timelike worldline (indeed most of the time philosophers think of time they’re imagining its passage along a single consciousness). The reason we accepted the idea of absolute time is because we thought we needed it to make any sense of the dimension of time, but it turns out this isn’t true. Recognizing this is a philosophical advance as well as a scientific one.
Extracting ontology from scientific theories is hazardous, but refusing to try–dismissing science as merely empirical as if anyone would devote time to it if we didn’t think we were pursuing the truth about things–is crazy. Why not take light cone structure to reveal the truth about temporal relations between events, as it seems to? There would be some weird consequences. Strictly speaking, what happens on Alpha Centauri (4 lt yr away) the day after the light that just reached us was emitted is not yet in our past. However, there is something close to a common rest frame between us, so a common solar system-Alpha Centauri time slicing of spacetime can be a useful construct. Another example is that no even that occurs inside a black hole billions of years old is ever in our past (assuming we never fall into said black hole). These ideas may take some getting used to, but I don’t see why they must be wrong.
Substances existing in time
One worthwhile objection is that, if a person thinks four-dimensionally, he will be led to the conclusion that his current body–himself as he is right now–is actually only a piece–an infinitesimal piece–of his 4D block body, just as his left half is only a piece of his body and not a whole. However, we experience ourselves at each given time as being complete. “Me now” is a very different thing than “my left half”. The former has beliefs, responsibilities, etc, while the latter does not. Indeed, this intratemporal completeness must indicate something profound, but I think it tells us something about substances (using this word, as usual, in the Aristotelian way) and how they relate to time rather than something about time per se. It does seem that a true substance always has an overall state, and this state is a function of proper time along its worldline but not spatial location within the substance (or else it wouldn’t be an overall state). This is presumably what makes absolute time theories credible–my body does have a frame (and I wouldn’t remain a substance for long if different parts of me were moving at relativistic speeds with respect to each other) and this is important for its persistence as a unitary entity.
Filed under: philosophy of science |