Under Construction

Change, and the Only Moment That Is Real

No man ever steps in the same river twice - Heraclitus - Plato's dialogue Cratylus

Back on the page about facts, a promissory note was left unpaid: the claim that, strictly speaking, only the present moment is real. It is time to make good on it - and doing so means saying what time actually is on this account. The answer is that time is not a stage the world plays out upon. It is something the world is endlessly making. There is no river of time that we drift along. There is only the world, producing its next moment, and the next, and leaving the spent ones behind.

Index

Three Tenses, Three Conditions

Why Only Now Is Real

The Near and the Far

The Moment of Decision

The Waterfall

Three Tenses, Three Conditions

Past, present and future are not three regions of one existing landscape, equally real, with us standing somewhere in the middle. They are three different conditions a thing can be in. The future is possibility: a spread of things that could come about, none of them settled, none of them yet a fact. The present is decision: the single moving edge where possibility is actually being turned into fact. The past is settlement: what has been decided, finished, and beyond all altering. Three tenses - but three genuinely different kinds of being, not three rooms in the one house.

Why Only Now Is Real

Recall what real was made to mean a few pages back. A thing is real when difference and change are part of what it is - when it sits somewhere, and that somewhere can change. Hold the three tenses up against that test, and only one of them passes. The past has finished changing; it is frozen into settled truth, perfectly true and never again to move, which is exactly why it is no longer real. The future has not begun changing; it is mere possibility, and possibility is not yet anything that could move. That leaves the present - the one place where change is actually under way - as the sole inhabitant of reality. Now is not just the most vivid moment. It is the only real one.

Now is the measurement that confers reality.

There is a sharp little consequence here. People worry about whether the future is fixed or open, as though it were a thing sitting in wait that might turn out one way or another. But the future cannot change at all - not because it is fixed, but because there is nothing out there yet to do the changing. You cannot alter what has not been produced. Changing is something only the present can do: it works on the possibilities the future offers and produces the facts the past will keep.

The future cannot change, because it has nothing to change from.

The Near and the Far

Not all of the future is alike, and the difference is worth having. The far future is loose: almost anything compatible with the present is possible out there, and nothing yet narrows it down - open possibility, barely shaped. The near future is a far tighter thing. As a moment draws close to the present it stops being vague and firms up into a definite envelope of weighted chances: this likely, that unlikely, the other ruled out. That envelope of imminent chances is what physics calls the wave function, and on this account it lives only here, in the near future, and nowhere else. The far future carries no wave, because it has not yet been brought to enough of a point. The difference between the two is not a difference of kind but of nearness - distance, as the diaries put it, is just detail.

The technical detail

A note against a tempting misreading. That the near future is a spread of weighted possibilities does not make those possibilities so many parallel realities, each as actual as ours. They are possibilities - information, not worlds. There is exactly one actual universe; the roads not taken had potential, and potential is all they ever had. Wishing the others into equal existence, as some readings of many-worlds and the multiverse do, is wishing for Father Christmas - a free lunch the bookkeeping never allows.

The Moment of Decision

So a moment arrives at the present as a tight envelope of possibilities and leaves it as a single fact. That collapse, from many to one, is what happens at Now, and it is the most consequential event there is, because it is where reality is actually made. The natural guess is that the chances themselves do the deciding - that the world rolls its weighted dice and takes whatever comes up. Virtualism says something more particular. What forces the resolution is not the probabilities but an imbalance: the clash, met several pages back, between a thing's inside and its outside, which cannot both be satisfied as matters stand and so must be settled one way or the other. The dice give the odds; the imbalance pulls the trigger. It is the same paradox-engine that has driven the whole story, now caught doing its work at the very finest grain, moment by moment.

And it works in whole steps. A thing does not change by a smear or a fraction; it shifts by a complete amount or not at all, because a half-change would leave it, in mid-step, no longer the whole thing it was. The world advances in definite clicks rather than a smooth glide - which is the deep reason physicists keep finding everything, at bottom, quantised. Each click is one possibility made actual: one more fact added to the total.

The Waterfall

The instant Now produces its fact, that fact is already sliding away. A new present forms on top of it, and the old one drops back - still perfectly true, still a fact for ever, but no longer real, no longer changing. Behind every passing moment streams an endless waterfall of spent facts, each one true and finished, not one of them real any more. Reality is never the whole river. It is only the bright leading edge, the thin line where the falling is actually taking place.

Which raises an obvious question. If facts only ever accumulate and never vanish, where does all that settled past go - and why does it still seem to bear on the present, so that nudging one thing here tugs, however faintly, on everything else? That weight of the gathered past turns out to have a name we already know. It is gravity, and it is where we go next.