Is Time Real?

McTaggart’s argument

Time and space• Time and space are ubiquitous, general features of our world.– Our experience of time and space are central to our cognitive lives as well.

– It is hard to imagine a world that is non-spatiotemporal.

• Nonetheless, it is not easy to say exactly what time and space are. – This requires a fair bit of reflection.

Time in particular• Time has some features that make it particularly interesting to reflect on:– It appears to be directed (from past to future)– It appears to pass or flow– It is closely connected to the concept of change.– None of these applies to space.

• These features make time seem more puzzling than space.

• In fact, they lead McTaggart to a very surprising conclusion.

Temporal concepts• McTaggart begins from a simple observation; we have two ways of thinking about time:

• The A-series: Times/events are divided into past, present or future.– Always changing: An event is first future, then present, and then past.

• The B-series: Times are related as earlier than, later than or simultaneous with. – Permanent: if x is earlier than y, it is never later or simultaneous with y. TAKE NOTE!

Both series• According to McTaggart, the existence of time requires the existence of both series.– Events are both earlier/later than each other, and past, present or future.

– On his view, time must be a hybrid, A-/B-series to be real.

• However, this does not mean that McTaggart sees both series as equal partners.– One is more fundamental than the other.– In fact, the A-series underlies the B-series.– For him, there could not be a B-series without an A-series.

Time and change• Why does he think the A-series is more fundamental? His argument: 

1. Change is essential to time2. In the B-series, there is no change.3. Time must be either an A-series or B-series 

• Therefore, 4. the A-series is required for time to exist.

• This argument is valid (if the premises are true, the conclusion must be true).– But are the premises true?– McTaggart defends #2 robustly.

Change and the B-series• Imagine a poker sitting next to the fire today but in the fire tomorrow– The poker being hot is later that its being cold.

• This statement is entirely in B-series terms.– Hence, it is permanent: if true, always true.– Therefore, there is no record of change here.

• There would be change, however, if the event of the poker being hot was not only later than the event of it being cold, but was also – first future, then present, then past.

An analogy• Consider the Greenwich meridian:

– At a certain place, P1, it is in England, at another place, P2, it is not in England.

• This is analogous to the poker:– At a certain time, T1, it is cold, at another, T2, it is not.

• But the Meridian does not change. – Hence, nobody should say that the poker, as described in B-series terms, changes.

Events and change• Consider any event; e.g. the death of Queen Anne. – Does this event ever change?

• McTaggart: No.– It was, is and will be a death.– It was, is and will be the death of a monarch.– It will never occur on any date other than 1-Aug-1714– Etc.– None of it’s properties change.

• There is one way it could change:– From future, to present to past

What the B-series entails

• Recall: B-series relations don’t change with time (they are not temporally variable).– So, if E1 is earlier than E2, this can not change.– I.e. “E1 is earlier than E2” is permanently true, if true at all.

• But note: if a proposition is true, there must be something that makes it true.– “John is in room 12” is true only if John himself is actually in room 12.

– This is often called the “truthmaker” principle.

• Accordingly, if “E1 is earlier than E2” is permanently true, whatever makes it true must permanently exist.– Hence, E1 and E2 can’t go out of existence.– All times/events are equally real on the B-series.

To sum up• McTaggart’s defence of premise #2:

• On the B-series, all alleged cases of change are logically analogous with non-change.

• Events don’t come into existence or pass out of existence on the B-series.

• Events don’t change on the B-series.

• Hence, premise #2 is right:– There can only be change if there is an A-series.– Hence, the A-series is more fundamental

Picturing the B-series• McTaggart: where’s the change?

BreakfastAwake This

lecture Dinner To bed

Later than

Picturing the A-series

• McTaggart: We need both series for change!– The absolute NOW gives meaning to change.

BreakfastAwake This

lecture Dinner To bed

Later than

NOWFuturePast

The main argument1.Time is real only if change is real;2.Change is real only if the A-series is

real;3.The A-series is contradictory;4.Since nothing contradictory can be

real,• Therefore, 5.Time is unreal.

• #3 is especially noteworthy.

Picturing the argument• Time depends on (entails) change, which depends on (entails) the A-series.

• So, if you knock out the A-series, everything else falls too.

Time

Change

A-series

McTaggart on the A-series

1. Past, present and future are incompatible properties.

2. But if the A-series is real, each event exemplifies all three properties.

3. But no event can have incompatible properties.

4. So, the A-series is contradictory.

– If E is present, it isn’t past/future

– If E is past, not present/future

– If E is future, not present/past

– Change requires this.– This is what it means to say that time passes.

– An a priori truth

An objection• McTaggart considers an obvious reply:

• No event has any two A-series properties at the same time!– E is present, will be past and was future– E is past, was present and future– E is future, will be present and past.

• There seems to be no contradiction here.

McTaggart’s reply• But now we have higher order A-series properties:

– was future, will be present, etc.  

• What does it mean to say, e.g., that E ‘was future’?– McTaggart: At a moment of past time, T, E is future.

• Problem: Each moment of time is past, present and future too.– So if T is past, it is also present & future: contradiction!

• Response: T is past, but was present and was future.–  No contradiction here.

• McTaggart: “T is past” means “T is present at a moment of past time, T1”. – But T1 itself must be past, present and future: contradiction again!

Vicious infinite regress

• McTaggart: We start with an apparent contradiction.– The obvious way to remove it leads to another contradiction.

– The obvious move to remove that, leads to another contradiction.

– And so on, and so on, …

• His conclusion: the attempt to make our description of the A-series coherent leads to an infinite regress; – This regress is vicious because the contradiction never gets removed.

Summing up• McTaggart: The A-series cannot be described without contradiction.– Hence, it cannot exist.– Hence, change cannot exist.– Hence, time cannot exist.

• Time is a kind of cognitive illusion.

C. D. Broad on McTaggart

• Broad makes a distinction:– Tensed copula:

•“It is raining”.•Equivalent to “It is now raining”.•Says something currently occurs.

– Tenseless copula•“3 is a prime number”•Not “3 is now prime”•Makes an eternal claim about the number 3  

• He agrees with McTaggart that tenseless claims are permanent, but he disagrees with McTaggart’s analysis of the A-series.

Broad’s evaluation• Broad: McTaggart makes an assumption that he never justifies.– He assumes that temporal claims must be analyzed into claims that have only:•A tenseless copula•Temporal properties (past, present, future)

• E.g.: “E was future” = “At T1 (a past time) E is future.– Note, “is” must be tenseless here.– To say that E was future is not to say that E is now future.

Broad observes• Broad: if we follow this analysis, then we do get a regress.– Every time is (tenselessly) past, present and future.

– And the time at which that time is past, will itself be past, present and future.

– And so on.

• But this doesn’t matter, so long as the properties can be had successively.

Time and space• Broad: I agree with McTaggart that the B-series on its own does not suffice for time:– It is static, directionless, just like space.

• So, any temporal concept must be an A-series concept.– This includes “succession”.

• By moving to a tenseless analysis, McTaggart is unable to analyze temporal concepts at all.– That’s why he runs into trouble.– But we can just avoid a tenseless analysis.

Broad’s analysis• Broad: tensed concepts such as “was”, “will be”, “soon”, etc. are all easily understood.– We can’t analyze them tenselessly:

•we’ve seen why.– We can’t analyze them tensedly:

•that would be circular.

• Hence, tensed concepts are primitive.– We don’t analyze them at all; – we just try to understand how they work.

How does this apply to McTaggart?

• Let’s go back to McTaggart’s regress argument– He thinks any event, E, must be past, present and future.

• Now go back to the obvious reply:– E is present, will be past and was future; or– E is past, was present and future; or– E is future, will be present and past.

• Broad: there is no need for further analysis.– Just stop here!– Certainly, no need to follow McTaggart’s tenseless analysis.

• This debate has led to two views on the nature of time, which we shall examine in coming weeks.

The current debateA-Theorists (e.g. Broad)• Time is real.• The A-series is fundamental.

• Time passes.

– Very few follow McTaggart in denying the reality of time.• Most, therefore, reject his hybrid A-/B-series view, and defend one or the other.

B-Theorists• Time is real.• The B-series is all that is needed for time to exist– B-relations are the only temporal properties.

• Time doesn’t pass.

Some questions1.McTaggart assumes that time entails

change. Is he right?2.What is McTaggart’s understanding of

change? Is he right?3.How does McTaggart conceive of the

present?4.Can you think of some reasons to

believe that the A-series is real?5.What would change look like on the B-

series?

Appendix: a different take on the argument

•McTaggart assumes every event must have all three A-properties, which seems fair. But why not explain how this could be as follows?– E is future at T1– E is present at T2– E is past at T3

•Answer: now A-series properties have been reduced to relations events have to times.– But these relations are temporally unchanging: if E is future at T1, that will never be false.

– Hence, this is just a B-series in disguise, so McTaggart will reject it.

•Question: why not resist McTaggart’s reasoning? Why not accept the B-series as the true nature of time?