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 paper 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
    Jan 16 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. Jan 17 at 19:35
  • Edit: only capitalised 'here's'.
    – Geoffrey Thomas
    Jan 19 at 15:40

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

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

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