Presentism describe how only the present exists, the future have yet to be actualised and the past has ceased to exist (except for its trace left behind in our memory at the present that allow us to deduce it once existed)

Now consider two presentists A and B. In the past, B have wrote a card to send to A. Now, A receives it and from the writing he knows B wrote that in the past.

However the above is in the perspective of A, thus to A, the present is right at when A read the card. But in B's perspective, the present is at B when he is writing the card.

So we now have the issue of two presents that are subjective to A respectively B, yet located at the future or past of B and A

  1. How to determine which present we should use as the "now"?

  2. Since to B, A is to the future of B, it basically have yet to come into existent in the presentist view, but is B also nonexistent to A since it is to the past of A?

NB The scenario is nonrelativistic in order to better probe the relations of the two presents, thus any answer invoking things like relativity of simultaneity is going to be missing the point


Under presentism there is only one now. From B's point of view the future in which A will receive the card does not yet exist. B relies on his observations of events which happened in the past but no longer exist to infer things which will happen in the future but which do not yet exist, such as A receiving the card. At the time of A's receiving of the card, the B that was sending the card at the time of its sending does not exist any more, since it was in the past. When the now was at the time that B sent the card both A and B existed, but A was not at that time receiving the card. At the time A receives the card, A and B both exist, but B was not at that time sending the card. If you have more than one now, I don't think you're talking about presentism any more.

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    So you mean instead of each person has a subjective now (which as you said will not be presentism), there's some kind of universal now that is like a scanner running across the timeline where the events A and B did are plotted (the description of timeline is added here as otherwise I have trouble figuring out where this (constantly moving) now is), and each of these events take turn to go from yet to exist, to presenting now to being past and ceased to exist depending on where they are relative to this now? – Secret Jun 8 '17 at 12:19
  • More or less, yes. We can't say that there is any 'timeline' that the 'scanner' is running across, since under presentism the only moment that exists is now. But other than that point, yes, you've got the idea. – Jesse Maher Jun 8 '17 at 12:27
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    Perhaps I should add, don't try to think of 'where' the now is. It is in the only place it can be, which is the present. – Jesse Maher Jun 8 '17 at 12:31
  • As an interesting aside, it might be interesting for you to look at the delayed choice double slit quantum eraser experiment. From what I can tell, this experiment empirically falsifies presentism by demonstrating backwards causation. – Jesse Maher Jun 8 '17 at 12:46

This is deep stuff. It is obvious (is it not?) that the past and future do not exist. Thus the present is all. Time would be psychological/conceptual as per Kant and the Buddha. From this we get to the 'Perennial Now' or 'Divine Instant' spoken of by mystics and meditators the world over, which would be consciousness free of time or instant and pure awareness, or the Biblical 'I Am'.

The difficulty is that the present has no duration. This means that while nothing can happen in the past or future there's not enough time for it to happen in the present. So to make full sense presentism we must deny the true or fundamental reality of events, which is just what the Perennial philosophy does.

Again I would recommend Hermann Weyl as a mathematician well on top of this one. He points out that the intuitive continuum, the continuum of experience, is not extended. It is always Now. It is the mathematical continuum, a product of imagination, that is conceptually extended.

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