Objection 1: No Real A-Series
As discussed in Chapter 1, Sextus Empiricus argued that time is not real because the past and future are unreal. Similarly, as discussed in the Chapter 6, duration and thus time are mind-dependent because, again, the past and future are unreal.
These challenges to the reality and mind-independence of time arise directly out of assuming presentism. If presentism is true, it is susceptible to these sceptical challenges. It cannot hold that time is real if only the present is real; time is primarily constituted by the past and future. Furthermore, many features of tense theory, such as temporal passage, are problematic given there is only present change, and no real past or future (Leininger 2015).
How can a presentist answer them? They can agree there is no time where time is something constituted by a past and future. However, this does not matter. Present features of the world explain why we can still talk about such times and something like a “duration”. We explore what such features might be in Chapters 5 and 6.
Objection 2: Presentism Lacks Truth-Makers For Truths About the Past
Presentism holds that the past is unreal. This is similar to merely possible or imaginary worlds (at least, given intuitive views of such worlds). Yet, we often make claims about the past that seem true. For example, it seems right that there were dinosaurs. If the past is unreal, then what makes statements about the past true?
An initial response is the dinosaurs in the past make it true. However, such truth-makers are not real, given presentism. Unlike, say, horses, there are no dinosaurs to make true our statements about them.
We might, instead, answer that signs or traces of dinosaurs make statements about them true—for example, fossils (e.g., Mellor 1981; Bigelow 1996). However, that only shifts the truth-maker to something specific in present things—the trace or sign—that point at the past. But what is it about the present truth-maker— such as the fossil—that makes true that there are dinosaurs? If the answer is simply that the fossil is a trace of dinosaurs, then the truth-maker once more contains past things (the dinosaurs that of which it is a trace).
According to Sider, these answers turn on cross-time relations, and presentism cannot work with such relations (Sider 1999, 327-331). Cross-time relations are relations that hold between my present belief in dinosaurs and past dinosaurs, or a present fossil and past dinosaurs. There are other kinds of cross-time relations involving truth-makers as well. For example, there are causal relations between a truth-maker that causes my perceptual belief in it (see Chapter 1).
One answer is that there is a past fact about dinosaurs. This tensed fact makes true beliefs about the past, much as perceptual beliefs are made true by truth- makers in the world. Just as the event of a distant thunderstorm can be a truth- maker for my perceptual belief that there is a thunderstorm, so the event of Jurassic dinosaurs roaming the Earth makes true my belief that there were Jurassic dinosaurs.
However, again, presentism denies the reality of the past; it denies the reality of dinosaurs. There cannot be real truth-makers with dinosaurs in them (such as their roaming around in the Jurassic period). Presentism cannot work with them because, no matter which time is considered present, the other time is unreal.
Some presentists do try to answer this by appealing to metaphysical entities. For example, Bigelow proposes necessary facts that, although not themselves past, are about the past, for example, there is present fact that there were dinosaurs. This is not a fossil or a perceptual belief. It is a fact of the universe itself (Bigelow 1996). However, the use of “about” here seems to have all the cross-time problems of traces and truth-makers. A present entity that must include the past in some way still needs to explain how it can do so without the past being real.
Others, “nefarious presentists”, argue that presentists should give up trying to sincerely answer this challenge. We can talk as if there are truth-makers, but we need not commit to their existence. Here’s Tallant and Ingram (2015):
[W]e advise presentists to be nefarious and to endorse both of the following
- (1) Truths about the past are expressed using primitive (and unanalysable) tense operators;
- (2) The primitive (and unanalysable) tense operators do not pick out some
distinctive ontological category, or aspect of reality.
In addition, one may answer these questions by answering them non- metaphysically—and instead, turn to the grammar of statements about the past.
This is to treat past talk, and talk of tensed facts, as primitively true or false; we discuss it further in Chapter 5.
Objection 3: Presentism and Physics
Presentism has problems with current physical concepts of time. Briefly, the distinction between the past, present, and future in current physics is relative to arbitrary and conventional frames of reference. Such frames are defined by one’s velocity. As such, tense distinctions are also defined merely by one’s frame of reference and velocity.
Given presentism, this means what is real or not is defined by one’s velocity, which is far from intuitive.
We discuss the consequences of relativistic physics in Chapter 4.