I know this question has been asked many times before but I'm honestly not capable of fully understanding all the many answers that have been given for questions like this. Basically I'm wondering when people talk about the A and B theories of time or similarly eternalism and presentism are they discussing what they believe "actual reality" is like or more so the most rational way to "think about" reality. Like as far as I understand B theory it says that there is truly no dynamic element to reality, that everything is static, and while I understand that that might be an accurate description of reality I just can't understand how people could accept such a "life changing belief" and continue to function. Wouldn't a believer of the B theory also believe that "their self" is bound to whatever present moment they're experiencing? Like I believe that everything is most likely predetermined and that doesn't stop me from being a productive member of society but if I were to fully believe that my personal subjective experience of life consisted of nothing but a "timeless ground hogs day" I don't think I'd be able to get out of bed. Like is my perception of the B theory completely incorrect or am I just much more emotional than other people who believe that the B theory of time makes sense? It just seems odd to me that the B theory seemingly implies that death or like eternal oblivion doesn't "happen" to any presently existing consciousnesses? Like am I taking the B theory in a much more literal way than it's intended to be taken? Like if all of time does exist "at once" if I'm to think of time in the exact same way as a dimension of space then wouldn't it imply that "my consciousness 5 minutes from now" is literally as existent as the me in this moment and that I am completely separate from my consciousness 5 minutes from now giving me no non altruistic meaning in my present actions? Like is eternalism and or the b theory of time meant to be taken in a complete literal sense because if so I just can't understand how anyone could accept something so "life changing" easily. Like if the b theory is correct then wouldn't dread or excitement be completely irrational to feel? Wouldn't "I" just be experiencing 4:55 am on 7/21/22 for a timeless "eternity" while other "iterations" or "versions" of this body or "me" are out there experiencing whatever moment they exist at? Sorry to anyone that reads this because I truly have no idea how to write anything I feel ashamed of myself for like submitting something so lackluster but this thought has been in my head 24/7 for a good 2 months quite literally 24/7 these past few weeks and I'm craving some sense of comfort.

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    It depends on who is discussing. McTaggart in his original presentation certainly meant to argue that B-theory is the "true" metaphysics. In contrast, some modern authors (e.g. Lombard) see it as a pointless debate about words. An intermediate pragmatic position is that while it is, ultimately, a debate about tense conventions, some are more expedient than others given the entirety of contexts where tenses are used, including action contexts that you worry about.
    – Conifold
    Commented Jul 21, 2022 at 9:30
  • this is a really dumb question but is metaphysics generally used to refer to concepts more so than other "non physical things" like aspects of conscious experience? like I've always thought of metaphysics as meaning existent in some way shape or form and non physical like the sensation of touching a cloth. Also this is off topic but I'm a but like i've seen your answers on this website before many times so i feel like im talkign to a celebrity right now man that sounds so unbelievably dumb but i feel like id rather say that than not Commented Jul 21, 2022 at 9:43
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    Metaphysics traditionally refers to studying the deep structure of everything that exists, incorporating physics, but speculatively going beyond what can be determined by scientific methods alone. But metaphysical perspective, the God's eye view, is disjoint from the life perspective we find ourselves in. This is why, and this is characteristic of philosophers and foreign to general public, whatever view (about the metaphysical nature of time or whatnot) they adopt has no tangible consequences for behaving in everyday life. They compartmentalize, that is the psychology of it.
    – Conifold
    Commented Jul 21, 2022 at 10:41
  • @crackheadhobo, there has been serious philosophical argument since the beginning of the 20th century over whether metaphysics is about anything at all or whether it's just word games. One reasonable position is that people who think they are arguing over the A and B theories of time are not arguing over what reality is like but only over how to visualize reality. Commented Jul 21, 2022 at 10:50
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    There is no reason to act differently than relevant experience suggests whatever "true" metaphysics happens to be like, if there is such a thing at all.
    – Conifold
    Commented Jul 22, 2022 at 5:12

3 Answers 3


Special Relativity in physics would seem to indicate that the B theory is true. 'Now' is defined differently depending on the observer's state of motion. So if you change which direction you are moving in, bits of 'the past' can suddenly become 'the future' again.

But I think your problem here is more emotional than intellectual. The B theory being true doesn't change anything about how you should live. Life is the same, it's just looking at it from a different perspective.

The past and future existing 'out there' all the time is really no different from other places existing 'out there' all the time. We sit on a boat floating down a river, and see the scenery change. One minute there are fields and meadows all around us, next minute, there's a city. The fields are still there, behind us. The city was always there, waiting ahead of us. It will still be there after we have passed it by. But the fact that everywhere we're not is still out there should make no difference to us because we are only living on the boat. We only experience the tiny bit of space close to the boat, and that's all we have to deal with. We know the rest of the universe is still 'out there', but it doesn't change our own experience.

We only ever experience 'here', just like we only ever experience 'now'. Other times and places exist, out of our sight, but there is no reason the other 'now's should bother us any more than the other 'here's do.

you mentioned the problem of identity over time, and whether you have any reason to care about your future selves. But this isn't specific to the B theory - we have the same issue even if time flows. Our sense of identity as a person comes from our memories, stored in the brain. If we 'swapped souls' - if the thing that has experiences moved from one body to another - then when you arrived in the new body you would think you was me, because you would have all my memories. You would notice nothing different, and be completely unaware of the change. Same if you jumped backwards or forwards in time. For all we know, we could be a different distinct person every moment, or all the same person, experiencing each moment in any order or all at once, or we can even posit a 'universal soul' that lives every life at every instant of its history, all at once. Not only are you all your past and future selves, but you are everyone and everything all at the same time. (This is something like the theory of panpsychism or even pantheism.)

If the possibility that all your different moments in time might be different selves depresses you, then maybe the equally possible possibility that we are all the same self - that not only should we care about all our past and future selves, but also each other - might cheer you up?

We have no way to tell. From the ultimate in atomised individuality to absolute cosmic unity - it is impossible to determine. So we had might as well pick whatever theory gives us the most comfort. It might, after all, be true!


I will give you a physicist's perspective. According to Special Relativity, we exist in a four dimensional 'spacetime', through which we coast inertially along our own personal time axis. Time can therefore be considered as a coordinate, t- one of four indicating your location in spacetime. Through your life, you coast through spacetime in the direction of increasing t, along a trajectory known as your world-line. Your past is a region of spacetime through which you have drifted- the present corresponds to your current position in spacetime, and the future is a region of spacetime you have yet to reach. Whether you consider future spacetime to exist already makes no difference to the fact that you have not reached it yet.

In your post, you refer to what I consider to be an extreme interpretation of time in which not only does future spacetime exist but also that all future events are already there at their allotted coordinates, which means that particles are 4d sausages occupying the entire length of their world-line, rather than being points that move along a world-line. There is nothing in physics that requires or supports such a view, which as you point out is also entirely at odds with our direct experience that we exist from moment to moment.

You might read statements to the effect that Special Relativity supports the idea of future events already existing, but that is true only in a very specific and largely meaningless sense, arising from the absence of absolute simultaneity. I can provide an explanation of that if you would like to ask a separate question about it (the answer is too long to slot in here).

The view of time I have summarised above also does away with the nonsense you will read about the grandfather paradox, self-consistency principles and so on. If you consider that all the particles that comprise the Universe are coasting forward in a direction of increasing time, then if you found a way to go back through spacetime to the point the Universe occupied 100 years ago you would not be able to kill your grandfather for the simple reason that he and the rest of the Universe are no longer there.


From Wikipedia : B-theory of time

B-theorists argue that the flow of time is only a subjective illusion of human consciousness, that the past, present, and future are equally real, and that time is tenseless

Note the "subjective" aspect. McTaggart's The Unreality of Time was published in 1908.

A method of describing the subjective aspect of time was also developed by Heidegger in Being & Time (1927), where the temporality of Dasein is defined similarly to the B-theory as "the unity of the three dimensions ... of future, past and present." i.e. Simon Critchley on Being & Time

The key to Heidegger's understanding of time is that it is neither simply reducible to the vulgar experience of time, nor does it originate in distinction from eternity. Time should be grasped in and of itself as the unity of the three dimensions — what Heidegger calls "ecstases" — of future, past and present.

The vulgar, ordinary meaning of time is what is collectively experienced as 'clock' time. The A-theory.

A time and B time can coexist, just as Heidegger's authentic and inauthentic temporalities do — i.e. from McTaggart's Views Revisited

McTaggart emphasizes that the B-series is not sufficient for the constitution of time, because the terms for “earlier” and “later” stem from our knowledge of the A-series. Moreover, the A-series is necessary for the constitution of time.

Note also, as clarified in chapter 3: The Investigation of Subjective Time, McTaggart's subjective B-series is in consciousness whereas Heidegger's authentic temporality is of Dasein, which is not the same as consciousness.

As for whether time exists at all in nature: Certainly in the Aristotelian sense, where there is movement there is time, but the point is moot unless there is someone to experience it. From that point it is a human construct, measured by convention. The interior, existential aspect of time is another concept altogether, useful for describing phenomenological existence and aspects of experience.

As for relativity: that just says absolute time (the present) — if it exists as a universal moment — is unobservable. Its existence can’t be proved or disproved. So relativity does not really impact on the A-theory/B-theory.

  • thank you so much for the answer. id heard many people say things such as relativity favors the b theory. wouldnt the b theory imply something like parmenide's unchanging reality? like in the sense that there is no change other than i guess what you could call conceptual change Commented Jul 23, 2022 at 4:59
  • I think Permenides' unchanging reality is raw nature. However, in Heidegger at least, time facilitates the Self (as movement of mind), then further, anticipation, intentions and experience, which use personal past, future (plans) & the present moment all together, in a unified interior temporality. (B-theory may differ, as an earlier theory, but it is still subjective/interior.) Subsequent devising of objective, scientific clock time is a separate collective enterprise: A-theory. Interior temporality doesn't extend to objective reality except for coinciding in action in the present moment. Commented Jul 23, 2022 at 11:05

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