Time, change and reality

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time, change and reality

McTaggart’s argument has divided philosophers into two camps on the nature of time:

A-Theory (Tensed theory of time)

  • The A-series (tense) is real

  • The A-series is the fundamental nature of time

  • Time is dynamic (passage is real)

B-Theory (Tenseless theory)

  • The A-series (tense) is unreal: it doesn’t mark a real distinction in time itself.

  • Time doesn’t pass

  • Time is nevertheless real

  • 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:

  1. The passage of time (as we have already seen)

  2. 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:

  • Events pass by “coming into being”

  • First they don’t exist (future)

  • Then they become real (present)

  • Then they…? Either become unreal again (presentism) or remain real (Broad)

This is the filmstrip analogy:

Unreal? Real Unreal


The B-series entails that all times are equally real:

  • If T1 is earlier than T2, it is always true that it is earlier.

  • Thus T1 and T2 must always exist in the B-series in order to have this relation at all times.

  • So, in the B-series, all times are equally real.

  • 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.


Prior: “present” = “real”; “Future/Past” = “unreal”
Prior on “real”:

  • It is a mistake to think that centaurs exist (are real) but in some “realm” of Greek mythology

  • Rather, what’s true is: some Greeks said/wrote: “Centaurs exist”

  • Unreality is not reality in some other “region”

  • If this were true, it would just be small-minded to single out reality as different from unreality

  • 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

  • B-theorist thinks past/future are just like the present, just in some other region

  • This misses the fact that the present is unlike other times

  • Only the present is real

Why is “present” the same as “real”?

Prior: because it too consists in a lack of prefix

  • Presentness of event = the event

  • E.g.: “My lecture is present” = “I am lecturing”

  • “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:

  1. Because time passes, every event is past, present and future.

  2. To avoid this contradiction, we say: “Every event is past, present or future at different times!

  3. 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:

  • What are we referring to when we speak in the past and future tense?

  • If past/future events don’t exist, how can talk about them be true?

  • E.g.: “W.W.II. was brutal”.


  1. Talk about past/future is untrue = skepticism.

  2. 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)

  • Present and past events are real

  • The future is unreal: there exists nothing after the present (that’s what makes it present)

  • 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.



What is change on this view?
Broad: three kinds of change:
Change in an object’s properties:

  • O was P at T1, Q at T2

  • 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:

  • Most fundamental

  • Explains the others (not vice versa)

  • “Becoming” = “coming into existence”

More on becoming

  • Future is not a property: nothing is future.

  • Future is a realm of non-being

  • The future is not “later” than the present: only existing things can have relations

  • Nothing ceases to exist

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:

  • They are neither true nor false

  • 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:

  • Yesterday I utter: “It will rain tomorrow”.

  • This is neither true nor false.

  • Today: it rains.

Question: is yesterday’s utterance still neither true nor false, or true?
If the former:

If the latter:

  • 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).

  • Absurd?

So, Broad’s position seems unsatisfactory.

A second problem:
2. What about M’s contradiction?

  • Even if no event is future, each is nonetheless present and past.

  • This is only consistent if it is present at one time, past at another.

  • But each time is past and present.

  • So each time is past at one time, present at another time.

  • But each of these times is past and present.

  • Etc. = infinite regress.


  • “Past at T” and “Present at T” never change in truth-value.

  • If true, always true.

  • 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:

  1. Change occurs

  2. On the B-series, change is impossible


  1. 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?

  • If an event is to retain its identity, it can’t have incompatible properties.

  • So an event can’t be past, present and future and remain identical through time

  • But it must retain its identity (otherwise it’s not one event passing in time).

Possible A-theorist reply
Temporal passage is just:

  • E’s time is (tenseless?) T1 and

  • T1 changes from future to present to past (the event remains the same).

B-theorist: This is circular! Time requires change but:

  1. Change is explained as passage

  2. 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

  • Reality as a whole does not change.

  • The B-series view is the view of all of reality.

  • But objects that exist within this reality do change.

  • 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:

  • Simple (unanalyzable into anything else)

  • 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!

  • B-series can’t explain our attitudes towards time.

E.g.: A painful dentist appointment awaits me on Friday:

  • Thursday, I fear the approaching pain

  • Friday, I suffer the present pain

  • Saturday, I feel relief at the receding pain – “Thank goodness that’s over!”

All of this:

  1. Seems rational: nothing wrong with these attitudes

  2. Can’t be justified if the B-series is true

Why not?

Ontological equality
On the B-series view, time doesn’t pass so:

  • If I am worried that the visit is approaching, I am worried about something that is literally false.

  • Similarly for my relief that it is receding.

B-series times are all equally real:

  • Past/present/future are not real distinctions

  • 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:

  • If this is why it is appropriate to feel relief and

  • This is true at all times

  • 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.

  • Like an object “changing” from left to right as I move.

We mistake this for temporal passage.

  • In fact, all that happens is a succession of psychological events

E1 E2 E3

Anticipate Experience Reflect

(Dread) (Suffer) (Relief)

T1 (Thurs) T2 (Fri) T3 (Sat)


A-theorist challenges
Why do we only remember earlier events, experience present ones and anticipate later ones?

  • How do we explain this if all events are equally real?

  • What in the world explains this if not passage?

B-theorist: causation:

  • Effects of an event are (effectively) simultaneous with the event:

  • So, they are experienced only when they (tenselessly) occur.

  • Later than an event, its effects become memories

  • 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:

  • 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:

  • This just means that the event is (entirely) located at a time (times) earlier than the time under consideration.

  • 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.

  • In fact, they have them successively.

Reply: Succession is a temporal notion:

  • It is the B-series relation of “later than” (or “earlier than).

  • So the A-series presupposes the B-series.

  • M is wrong to assume that the A-series is conceptually more basic.

  • In fact, it is the B-series that makes the A-series possible, not vice versa.

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