This is going to sound silly but I was wondering why McTaggart's approach is needed to prove time to be real/unreal.

Here's what I was thinking:

The existence of time is a necessary condition for there to be real change, thus the existence of real change is a sufficient condition to show that there is real time.

Which is I believe what McTaggart has as his first premise. But then wouldn't it be sufficient for one to show that there is/is not real change in order to show the (un)reality of time? Why does change have to be described by any of the A,B and C series in order for change to be real?

  • update: I believe that in McTaggart's 1908 work where he first argued for the unreality of time the definition of reality was never given. I take his reality to mean mind-independent existence, but if you have any suggestions please let me know!

  • update again: I see what you mean!! Sorry for being slow. Personally I think that temporal passage doesn't have to be real for time to be real, so I guess I take the B-theorist view. I see now how my stance on this issue will answer my own question: if I am a B-theorist, then of course I will think that just proving that there are real changes is enough to show that time is real, so I won't need to go through the following analysis like McTaggart did. But McTaggart needs more to show that time cannot be real as he holds that temporal passage is intrinsic to time.

Please feel free to point out what I've missed!

Many thanks for any help!

Best wishes,


  • Could you please give a definition for "reality" first? What do you mean by "real"?
    – OmG
    Commented Jan 16, 2021 at 18:58
  • You still need to say what you think un/real time is before we can know whether to bring McTaggart into it. Bear in mind that he was much exercised by apparent difficulties in considering the flow of time vs. a static division of time. Your version might lead to the one being real but not the other. Commented Jan 17, 2021 at 19:35
  • Edit: only capitalised 'here's'.
    – Geoffrey Thomas
    Commented Jan 19, 2021 at 15:40

2 Answers 2


Time on itself is an subjective experience, just a description for how we observe how the world around us changes. The reason we observe time as we know it, is because our neural networks have regression. That means that we can memorize things from the past, and use it now to our advantage. If we could not memorize or notice things from the past, we would not know that time existed, if it even existed.

If we were just a brain in a vat thats being put in memory of the past which 'did not exist', you could argue that time still existed, because the calculation used to calculate the present would still need the past to be calculated first.

That means, if time can't be calculated backwards, the past is calculated to get to this point, or there is no past, such as at the 'beginning' of the universe, where math starts to break down. In that calculation, things are simulated, and that simulation is the past.

So if time can't be calculated backwards, it is 'real' in my eyes(and the past has existed).

fun to read too: https://www.quora.com/Did-the-past-really-happen

  • 1
    And, McTaggart..?
    – CriglCragl
    Commented Jan 29, 2021 at 12:44

McTaggart's argument on the unreality of time, as per Wikipedia, depends on a contradiction revolving around past, present, and future.

Contradictions, for them to be meaningful, depend critically on time (simultaneity being an essential component) being real.

In short, McTaggart's argument fails for the simple reason that if time weren't real, there can't be contradictions, and if there can't be contradictions, you can't use contradictions to prove a point which is precisely what McTaggart's argument does.

  • 2
    Do you distinguish contradictory claims from contradictions in reality itself? In terms of claims, if you say "1+1=2" and I say "1+1=3" then our statements obviously contradict each other, but what does time have to do with it, isn't my statement just wrong for all time, and yours right for all time? And if you think there are contradictions in reality itself, what reason do you have to believe this? Something being true at one time and false at another doesn't seem like a contradiction in reality itself any more than "the walls are blue" being true in one room of a house, false in another.
    – Hypnosifl
    Commented Feb 23, 2022 at 18:20
  • Contradictions are time-bound, for a contradiction to be one i.e. for it to possess logical force, it must be "both in the same sense and at the same time". I am hungry at 12 noon and I'm not hungry at 3 PM is not a contradiction. However, I'm hungry at 12 noon and I'm not hungry at 12 noon is a contradiction. Commented Feb 24, 2022 at 5:38
  • 1
    I think "same sense" already rules out all possible differences in context, there's nothing special about time in this respect. If a person saying "I'm hungry" and "I'm not hungry" at different times, that difference in time is a type of contextual difference that means they have not asserted that a statement is true and false in the same sense. Likewise if a person at one location in space says "the walls are blue" and a person at another location says "the walls are not blue", that difference in position is a contextual difference, so they are not saying opposite things "in the same sense".
    – Hypnosifl
    Commented Feb 24, 2022 at 5:47

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