Abstract
Some theories of time entail that the present can change before or after it has happened. Examples include views on which time-travelers can change the past, the glowing block theory, Peter Geach’s mutable future view, and the moving spotlight theory. This paper argues that such ante factum or posthumous change requires a heterodox “split time” view on which earlier-than is not the converse of later-than.
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Notes
See Deasy (2015) for a recent defense and references. Not everybody understands the spotlight theory in this way. Cameron (2015) calls himself a moving spotlighter but does not think that there is an intrinsic property of presentness. On the other hand, Baker’s (2010) “BA Theory” is a variant of the moving spotlight in the sense intended here, even though she does not characterize her view in this way.
Some tenseless theories regard instants of time as metaphysically basic entities while others identify them with classes of events, or aggregates of temporal parts (Meyer, 2011a). These details do not matter here.
See Rescher and Urquhart (1971, ch. VI).
Kripke (1965) surveys the pathologies of non-normal systems.
The CLAUSES do not take a stand on whether the contents of utterances are temporal or eternal propositions (Richard 1981; Brogaard 2012). Nor do they tell us whether tensed and tenseless sentences are inter-translatable without loss of meaning (Oaklander and Smith 1994; Jokić and Smith 2003). The CLAUSES spell out the conditions under which tensed sentences are true at a time, which is not the same as specifying the content expressed by an utterance of a tensed sentence at a time. For example, we can accept that \({\mathsf {F}}\varphi\) is true at t iff \(\varphi\) is true at a time \(t'>t\), and still deny that this is what is meant by an utterance of \({\mathsf {F}}\varphi\) at t. (The utterer might not know what time it is.) Not every utterance at a time is about that time, even if the time of utterance is part of its truth conditions. What to say about the contents of utterances is a nice question but there is no need to settle this issue here.
The proofs can be found in Meyer (2009). One can establish similar results for ersatz views that treat times as maximal consistent temporal propositions (Fine, 2005, ch. 4) or as maximal coherent collections of tensed facts (Fine, 2005, ch. 8). Just as stronger systems of modal logic impose structural constraints (such as reflexivity, transitivity, etc.) on the accessibility relation between possible worlds, there are stronger systems of tense logic that impose various structural constraints on the temporal order relations. See Burgess (1984; Meyer (2011), or Müller (2011) for a survey.
Geach does not seem to appreciate this point. In Geach (1977, p. 53) and elsewhere, he endorses anti-realism about the future, which does not allow \({\mathsf {F}}\varphi\) to switch from false to true, as required by his account of prevention. In my view, this is part of what ultimately makes his position untenable.
Of related interest is the temporal knowledge argument in Perry (2001).
This is similar to the modal case, where Adams (1974) argues that there is no difference between what is possibly the case and what is possibly actual.
Skow postulates conceptually primitive hyper-tense operators, as part of his ideological commitments, but does not want to incur ontological commitment to hyper-times, something that he calls “clearly ridiculous” (2015, p. 49). This makes no difference to the argument. As noted in Sect. 2, any plausible account will give us both tense operators and times. The problem we are facing has nothing to do with which of them is more fundamental. The problem is that the real tense operators would have to track the movement of the spotlight of presentness, if there is such a thing.
There is also room for a view that rejects only one of the conditionals in CONVERSE. The validity of \(\varphi \rightarrow \mathsf {GP}\varphi\) corresponds to \(t' > t\rightarrow t < t'\) while the validity of \(\varphi \rightarrow \mathsf {HF}\varphi\) corresponds to the converse conditional \(t < t'\rightarrow t' > t\). The split-time view is thus a conjunction of two theses that can be accepted and rejected independently of one another.
See also Meiland (1974).
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Acknowledgements
Earlier versions of this paper were presented at The Metaphysics of Time conference in Aalborg in March 2019, at the meeting of the Philosophy of Time Society in Philadelphia in January 2020, and at the Third Venice–Lugano Workshop in February 2020. I would like to thank Giacomo Andreoletti, William Lane Craig, Steven Savitt, Giuseppe Spolaore, and the audiences at the three conferences for very helpful discussions and feedback.
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Meyer, U. The Future of the Present. Erkenn 89, 463–478 (2024). https://doi.org/10.1007/s10670-022-00540-y
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DOI: https://doi.org/10.1007/s10670-022-00540-y