- I once hoped that this book could be a modest revision of my "Mellor (D.H.) - Real Time", first published in 1981 by Cambridge University Press. But it should always have been obvious that this was a forlorn hope. Changes in my own views and the flood of new work in the philosophy of time — see for example Oaklander and Smith (1994) — have forced me to rewrite that book almost completely. While enough of its main claims and arguments survive to justify calling this book Real Time II, this is a new and self-contained work. So to avoid distracting readers by noting changes in the body of the work, I shall, for the record, summarise the main ones here.
- In "Mellor (D.H.) - Real Time" I followed the custom of calling temporal locations like past, present and future ‘tenses’, while distinguishing them of course from the corresponding forms of English verbs. However as failure to observe this distinction still vitiates much philosophy of time, I here call these locations ‘A-times’, adapting from "McTaggart (J. McT. E.) - The Unreality of Time" (1908) the now standard distinction between his A and B series, which I explain in chapter 1 ("Mellor (D.H.) - Past, Present and Future"). For the same reason I now call my theory of time a ‘B-theory’ and my main opponents ‘A-theorists’. The terms ‘tensed’ and ‘tenseless’ I confine to their original, proper and trivial grammatical uses.
- In chapter 2 ("Mellor (D.H.) - Truths and Truthmakers") I make more explicit what all serious A- and B-theorists mean by debating the ‘truth conditions’ of beliefs about the past, present and future. A common but vacuous use of ‘truth condition’, which lets beliefs have both A- and B-truth-conditions, can easily make our debate look pointless. But it is not. For what both parties mean by a belief’s truth condition is its so-called ‘truthmaker’, i.e. what in the world makes it true. What we disagree about is whether A-facts or B-facts — in the substantial sense of ‘fact’ for which I now argue explicitly — make temporal beliefs true. This is a real issue, for if B-facts do this job, A-facts do not; and if they do not, then they do not exist, since this is what they2 exist to do.
- In "Mellor (D.H.) - Real Time" I defended the token-reflexive view that an A-proposition like ‘e is present’ is true at a B-time t if and only if a token of it — e.g. a statement of it, or someone’s belief in it — at t would be true. But Quentin Smith (1993a3 chapter 3) and others have shown that this cannot cope with propositions like ‘there are no tokens now’, which can be true even though they can have no true tokens. So in chapter 3 ("Mellor (D.H.) - Tokens and Times") I now advocate the simpler view that ‘e is present’ is made true at t by e’s being located at t, and similarly for other A-propositions.
- Chapter 4 ("Mellor (D.H.) - The Presence of Experience") contains a new response to the claim in "Prior (Arthur N.) - Thank Goodness That's over" (1959) that B-theorists cannot make sense of people thanking goodness that something, e.g. a pain, is past. My old response was shown to be inadequate by the late and sadly missed Murray Macbeath (19834), who also showed me how to correct it. Following him I now exploit the fact that whenever we thank goodness for something’s being past, what makes us do so is not that it is past but that we believe it is; so if, as I argue, we B-theorists can say in B-terms what any such A-belief is, and what makes it true, we can make as much sense as A-theorists of our gratitude for (or any other propositional attitude to) the truth of any A-proposition.
- Spatial analogues of A- and B-theories are developed in chapter 5 ("Mellor (D.H.) - Time and Space") much as in "Mellor (D.H.) - Real Time". The main addition is a short section (for which I am indebted to Sir Martin Rees) showing that modern cosmology does not, as some A-theorists suppose, undermine objections to A-theories based on the special theory of relativity. Far from yielding a privileged reference frame and hence absolute simultaneity across space, its uniform treatment of the expansion of the universe implies that there is no such thing.
- In chapter 6 ("Mellor (D.H.) - Thinking in Time") I answer an objection in David Kaplan’s (19895) to my theory that a sentence like ‘Jim races tomorrow’ means a function from any time t to its truth condition at t, namely that Jim races the day after t. Among B-theorists the issue is merely terminological — should this function or its values be called the sentence’s ‘meaning’? — but here it is more than that. For by taking it for granted that A-sentences are made true by B-facts like Jim’s racing on 2 June, rather than A-facts like Jim’s racing tomorrow, Kaplan begs the question against A-theorists, as I do not.
- To my development and defence of McTaggart’s argument against A-facts in chapter 7 ("Mellor (D.H.) - McTaggart's Proof") I have added a rebuttal of Michael Tooley’s (1997) new theory of time. This admits only B-facts, while denying, unlike most B-theories, that they all exist at all times (on the grounds that B-facts about an event e come to exist only when e does), so that the universe of facts grows over time. This I argue, besides contradicting relativity (as Tooley admits), can appeal only if we confuse e’s being located at t with its existing at t. Even if the former is what makes ‘e exists at t’ true, e’s existence at t will still make both ‘e exists’ and ‘e exists at t’ true at all times.
- The B-theory of change in chapter 8 ("Mellor (D.H.) - Change") differs in one major way from that given in "Mellor (D.H.) - Real Time". There I argued that any changeable property F (e.g. a temperature) of a thing a is a relation a has to any B-moment t when it is F.
- I am now persuaded that this is wrong. However, I still reject the orthodox B-alternative that F is a property of a temporal part of a, namely a-at-t, since I still deny that things, as opposed to events, have temporal parts in any serious sense. I argue instead that a’s being F at any t is a B-fact whose only constituents are a and F — the time t being not a constituent of this fact but merely its temporal location. This, by making F what it seems to be, a non-relational property of a itself, stops changes in a reducing either to a’s being differently related to different times or to different temporal parts of a having different properties. That in turn shows why change, so understood, has no spatial counterpart, thus making time as much the dimension of change on my B-theory as it is on any A-theory.
- In "Mellor (D.H.) - Real Time" I took Davidson’s ("Davidson (Donald) - Causal Relations") view of causation6 as a relation between particular events. Now, for reasons given in my The Facts of Causation7 (1995 chapter 9) and summarised here in chapter 9 ("Mellor (D.H.) - Events, Facts and Causation"), I think causation8, if it relates anything, relates facts, like the fact at t that a is F. This simplifies my B-theory of the relation between causation9 and time, notably by putting the causation10 of stasis — a’s being F at a later t’ because it is F at t — on a par with that of change. It does however require a parallel treatment of the earlier—later relation, as holding between facts rather than between events or times. This is argued for in chapter 10.4 ("Mellor (D.H.) - Causation and Time"), where I infer on the one hand that events cannot be spacetime points or regions, and on the other, with Leibniz (1717), that it makes no sense to imagine everything happening ten minutes later, say, than it actually does.
- The main argument of chapter 10 ("Mellor (D.H.) - Causation and Time")is that causation11 is what distinguishes time from space and gives it its direction; in short, that time is the causal dimension of spacetime. Much of this argument follows "Mellor (D.H.) - Real Time", but there are three important additions. In §3 I dispose of apparent cases of simultaneous causation12. In §5 I show how time’s being the dimension of causation13 makes it also what Kant ("Kant (Immanuel), Kemp Smith (Norman) - Immanuel Kant's Critique of Pure Reason", B50) calls ‘the form of inner sense’. (This supersedes a related but weaker argument in "Mellor (D.H.) - Real Time".) And in §6, influenced by Robin Le Poidevin (1991 chapters 5-8), 1 show why the need for causation14 to preserve the identity of a thing through changes in its properties restricts change to the causal dimension of spacetime.
- In chapter 11 ("Mellor (D.H.) - The Direction of Time") I amplify my rebuttal in "Mellor (D.H.) - Real Time" of the still widely-held view that it is not causation15 but irreversible processes which give substance to the difference between earlier and later and thus give time its direction. I also simplify my causal explanation of our experience of the direction of time (as an accumulation of memories, of memories of memories, and so on) and my demystification of forward time travel16.
- The case in chapter 12 ("Mellor (D.H.) - The Linearity of Time") against causal and hence timelike loops differs from that in "Mellor (D.H.) - Real Time". There it derived from Michael Dummett’s ("Dummett (Michael) - Bringing About the Past", 1964) argument against backward causation17. I have now replaced that argument’s epistemic assumptions with the assumption, argued for in chapter 2 of The Facts of Causation18, that effects have chances, with and without their causes, which are real possibilities of their occurring in the relevant circumstances. (Thus for Jim’s smoking, C, to cause him to get cancer, E, his metabolism must give him chances of getting cancer both if he does and if he does not smoke.) I also argue for my previously tacit assumption that, as all agree, a causal relation has only two terms. This requires the fact that C causes E, and so E’s chances with and without C, to be logically independent of C’s causes, and so in particular of C’s chances with and without E. But I show that, if there were causal loops, these chances would not be independent; so there can be no such loops, and therefore neither backward causation19 nor circular time. This, on my reading of chances as real possibilities, validates the old but much-maligned objection to backward time travel20: namely, that if Dr Who, say, could travel into his past he could kill his grandmother in her infancy and so make his trip impossible, which is absurd. And so it is.
- I owe much to many people for ideas and arguments about time and related matters that have influenced the contents of this book. Relevant work in English published after "Mellor (D.H.) - Real Time" is included in the Bibliography. Besides those mentioned above, I am especially indebted21 to the work and comments of L. Nathan Oaklander, and also to Alexander Bird, Jeremy Butterfield, Max J. Cresswell, Kenneth Denbigh, Heather Dyke (And see also22?), John Earman, David Farmer, Jan Faye, William Grey (formerly William Godfrey-Smith), Katherine Hawley, Mark Hinchliffe, Ian Hinckfuss, Arnold Koslow, John Perry, David Lewis, E.J. Lowe, J.R. Lucas, G.C. Nerlich, Eric Olson, L.A. Paul, Huw Price, Graham Priest, Hans Reichenbach, Peter J. Riggs, Gonzalo Rodriguez-Pereyra, David H. Sanford, Kieran Setiya, Lawrence Sklar, J.C.C. Smart, J.W. Smith, Paul Teller, Michael Tooley, Susan Weir and J.T. Whyte.
- Finally, … [snip] …
→ Cambridge March 1998
Footnote 1: Explains the changes since "Mellor (D.H.) - Real Time".
Footnote 2: Is this conditional referring to A-facts or B-facts? Or is it rhetorically referring to either, whichever should be correct? Mellor, at any rate, claims that so-called A-facts – ie. past, present and future – do not exist.
Footnote 3: Sadly, I don’t have this, or other papers mentioned but not explicitly referenced by links within my website. What I do have by these authors is indicated in the links from the acknowledgement list Mellor gives at the end of this Preface, except when they are not mentioned there, when they appear in footnotes like this with a link like this – Quentin Smith.
Footnote 4: Sadly, I don’t have this paper. See Murray MacBeath.
Footnote 5: Sadly, I don’t have this paper. See David Kaplan.
Footnote 21: A similar list appeared in "Mellor (D.H.) - Real Time: Introduction and Summary".
Footnote 22: And also Heather Morland-Dyke?
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