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McTaggart’s argument has divided philosophers into two camps on the nature of time:
A-Theory (Tensed theory of time)
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The A-series (tense) is real
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The A-series is the fundamental nature of time
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Time is dynamic (passage is real)
B-Theory (Tenseless theory)
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The A-series (tense) is unreal: it doesn’t mark a real distinction in time itself.
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Time doesn’t pass
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Time is nevertheless real
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B-series relations are all there is to time
Today let’s look at the various arguments for and against each view of time.
First …
Time, tense and reality
Two issues separate A-theorists and B-theorists:
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The passage of time (as we have already seen)
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The reality of the non-present
These two are connected. Let’s see how:
Temporal Becoming
Important question: Just what is the passage of time?
One answer: temporal passage = becoming:
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Events pass by “coming into being”
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First they don’t exist (future)
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Then they become real (present)
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Then they…? Either become unreal again (presentism) or remain real (Broad)
This is the filmstrip analogy:
Unreal? Real Unreal
   
Becoming
The B-series entails that all times are equally real:
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If T1 is earlier than T2, it is always true that it is earlier.
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Thus T1 and T2 must always exist in the B-series in order to have this relation at all times.
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So, in the B-series, all times are equally real.
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On the B-series, there can be no “becoming”, no ceasing to be of events, no coming into existence of events.
I.e.: If you think that not all times are equally real, then you must defend an A-series view of time.
Arthur Prior does.
Presentism
Prior: “present” = “real”; “Future/Past” = “unreal”
Prior on “real”:
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It is a mistake to think that centaurs exist (are real) but in some “realm” of Greek mythology
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Rather, what’s true is: some Greeks said/wrote: “Centaurs exist”
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Unreality is not reality in some other “region”
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If this were true, it would just be small-minded to single out reality as different from unreality
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But it is different
Unreality is reality with a prefix:
Reality = no prefix: “really” is redundant, i.e., “I really lecture” = “I lecture”
Prior on time
Prior: The same applies to time
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B-theorist thinks past/future are just like the present, just in some other region
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This misses the fact that the present is unlike other times
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Only the present is real
Why is “present” the same as “real”?
Prior: because it too consists in a lack of prefix
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Presentness of event = the event
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E.g.: “My lecture is present” = “I am lecturing”
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“Present” is redundant – it adds nothing; it just is reality.
What’s present is always changing: therefore presentism entails passage.
Presentism and McTaggart’s Argument
Presentism seems bound to run up against McTaggart’s argument:
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Because time passes, every event is past, present and future.
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To avoid this contradiction, we say: “Every event is past, present or future at different times!”
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But the only time that exists is the present. There are no other times at which an event can be past/future. So:
How does presentism avoid contradiction?
Possible response: well, since only the present exists, there are no times at which an event is past or future. So, McTaggart’s contradiction never arises.
Problem: if there are no times at which the event is past/future, how does time pass? What exactly is temporal flow?
More problems with presentism
If past and future are unreal:
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What are we referring to when we speak in the past and future tense?
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If past/future events don’t exist, how can talk about them be true?
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E.g.: “W.W.II. was brutal”.
Options:
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Talk about past/future is untrue = skepticism.
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Talk about past/future is actually about present evidence (photographs, memories, etc.) = verificationism.
Problems: (1) is very rash: accepting skepticism to hold on to a theory of time counts against the theory.
(2) What are photographs, memories, etc. records of if there are no past/future events to which they might refer?
There are alternative A-theories.
The empty future (Broad)
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Present and past events are real
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The future is unreal: there exists nothing after the present (that’s what makes it present)
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Passage is the successive addition of “slices” of existence to reality
When an event becomes past, all that has happened is that new reality has been added after it: the more slices, the further in the past.
T1
T 2
T 3
T 4
Etc.
What is change on this view?
Broad: three kinds of change:
Change in an object’s properties:
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O was P at T1, Q at T2
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There was a time when reality included O being P but not O being Q.
Change from present to past: -
Occurs as new slices of reality are added
Change from future to present:
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Most fundamental
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Explains the others (not vice versa)
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“Becoming” = “coming into existence”
More on becoming
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Future is not a property: nothing is future.
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Future is a realm of non-being
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The future is not “later” than the present: only existing things can have relations
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Nothing ceases to exist
Problem:
1. What, then, are we talking about when we talk about the future: all such talk must be empty!
Are we facing the skepticism/verificationism choice again?
Statements about the future
Broad: There are no future facts to make these statements true or false, so:
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They are neither true nor false
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They just describe properties (they don’t actually refer to any!) and claim they might/might not become.
When a future fact (slice of reality) comes into existence, then the statement becomes either true or false.
Problem with this position:
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Yesterday I utter: “It will rain tomorrow”.
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This is neither true nor false.
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Today: it rains.
Question: is yesterday’s utterance still neither true nor false, or true?
If the former:
If the latter:
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Then a single utterance can be both true (what it said would come to pass did) and not true (i.e. neither true nor false, as it was yesterday).
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Absurd?
So, Broad’s position seems unsatisfactory.
A second problem:
2. What about M’s contradiction?
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Even if no event is future, each is nonetheless present and past.
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This is only consistent if it is present at one time, past at another.
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But each time is past and present.
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So each time is past at one time, present at another time.
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But each of these times is past and present.
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Etc. = infinite regress.
Also:
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“Past at T” and “Present at T” never change in truth-value.
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If true, always true.
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This is just the B-series in disguise.
So both models of dynamic time seem to have problems. Are there other arguments for the A-series?
A-series and change
An argument for the A-series:
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Change occurs
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On the B-series, change is impossible
Therefore:
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Time must be an A-series
But what kind of change does the A-series really provide?
All events change from being future to being present to being past.
B-theorist: What about Leibniz’s law?
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If an event is to retain its identity, it can’t have incompatible properties.
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So an event can’t be past, present and future and remain identical through time
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But it must retain its identity (otherwise it’s not one event passing in time).
Possible A-theorist reply
Temporal passage is just:
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E’s time is (tenseless?) T1 and
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T1 changes from future to present to past (the event remains the same).
B-theorist: This is circular! Time requires change but:
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Change is explained as passage
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Passage explained as (a kind of) change
Therefore, change and passage are never really explained at all.
Okay, but how does the B-series view explain change?
B-series change
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Reality as a whole does not change.
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The B-series view is the view of all of reality.
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But objects that exist within this reality do change.
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E.g. John is hungry at T1, full at T2
A-theorist: But what distinguishes this from spatial variation, which isn’t change?
B-theorist: Earlier/Later is experientially:
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Simple (unanalyzable into anything else)
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Qualitatively different from the experience of left/right
In other words, we can just “see” (experience) that they are different.
Problem: Does this really explain anything? How could we prove that this difference isn’t an illusion?
“Thank Goodness”
A-theorist: Experience actually favors my view not yours!
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B-series can’t explain our attitudes towards time.
E.g.: A painful dentist appointment awaits me on Friday:
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Thursday, I fear the approaching pain
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Friday, I suffer the present pain
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Saturday, I feel relief at the receding pain – “Thank goodness that’s over!”
All of this:
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Seems rational: nothing wrong with these attitudes
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Can’t be justified if the B-series is true
Why not?
Ontological equality
On the B-series view, time doesn’t pass so:
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If I am worried that the visit is approaching, I am worried about something that is literally false.
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Similarly for my relief that it is receding.
B-series times are all equally real:
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Past/present/future are not real distinctions
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So it is never appropriate to have attitudes that depend on them
B-series relations are permanent:
It is true before the pain that Sat. is later than the pain. But:
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If this is why it is appropriate to feel relief and
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This is true at all times
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Then it is appropriate to feel relief before the pain – this is absurd
B-theorist responds
Passage is psychological:
My attitudes to events are different at different times. The events don’t change, just my perspective.
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Like an object “changing” from left to right as I move.
We mistake this for temporal passage.
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In fact, all that happens is a succession of psychological events
E 1 E2 E3
A  nticipate Experience Reflect
(Dread) (Suffer) (Relief)
T1 (Thurs) T2 (Fri) T3 (Sat) Dentist
A-theorist challenges
Why do we only remember earlier events, experience present ones and anticipate later ones?
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How do we explain this if all events are equally real?
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What in the world explains this if not passage?
B-theorist: causation:
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Effects of an event are (effectively) simultaneous with the event:
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So, they are experienced only when they (tenselessly) occur.
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Later than an event, its effects become memories
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Earlier than an event, we can only anticipate (no backward causation)
To consider: can we explain why causes only precede their effects if past and future are equally real?
Ceasing to exist
On the B-series view of things, events never cease to exist in the following sense:
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No longer being a part of reality (because events always exist at some time or another).
However, it is perfectly fine to say that something ceases to exist:
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This just means that the event is (entirely) located at a time (times) earlier than the time under consideration.
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E.g. the pain has ceased = the pain event is earlier than the time at which I am speaking
Is the B-series is more basic?
McTaggart: A-series predications are contradictory.
Broad: only if we assume they are had at the same time.
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In fact, they have them successively.
Reply: Succession is a temporal notion:
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It is the B-series relation of “later than” (or “earlier than).
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So the A-series presupposes the B-series.
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M is wrong to assume that the A-series is conceptually more basic.
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In fact, it is the B-series that makes the A-series possible, not vice versa.
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