Growing block, shrinking block, and the conservation of reality

Ken writes:

Philosophers use the image of a growing block to think about the nature of time. It is one of several images. The image captures the steady accretion of past events as present moments become past moments. On a growing block conception of time, only the past and present are real as the future has not yet been determined. It is genuinely open. Against this, we could set an image of time as static with all events past present and future laid out in a great line. This is called the B-series conception of time. The events are ordered relatively earlier or later than each other, but not essentially as past present and future as such. The present is where we are on the line, and past events are earlier than now and future events are later. On this conception, the future events are already there, so this picture seems inconsistent with the openness of the future. The future is fixed. A shrinking block would be a conception of time whereby only the future and present existed not the past. The block shrinks as each present moment disappears into the past. For completeness, let me mention the pure presentist position that holds that only the present moment and neither the past nor the future exists. The philosophy of time is fascinating because none of these positions seems obviously and unproblematically right.

I’ve had a couple of occasions recently to ask visiting speakers, experts on the philosophy of time, for their take on an intuitive aversion I feel for ‘growing block’ theories of time. It’s quite puzzling and disorientating, really, because philosophical arguments are often based on strongly held intuitions, as the following objection is for me, but no one else shares it. It’s like I hit a wall.

For me, there can be no question of the growing block or shrinking block conceptions of time. These positions are ruled out by “the principle of conservation of reality” (which is just a grandiose name for something I made up). Put crudely, I can’t accept these pictures because I want to know, for the growing block, where the new events come from, and for the shrinking block, where the events go to. This really is the naive question it seems to be.

The growing block conception envisages a steady accumulation of events. What’s an event? I assume it’s some kind of arrangement of objects, properties and times. Can an event contain an object that doesn’t exist as a part? Presumably not. What would it contain, if the object didn’t exist? (I used to believe in non-existent objects and when I did, all these ontological questions had a particular significance for me). So, for me anyway, it seems natural to say the event of Wellington and company defeating Napoleon and company at the battle of Waterloo contains among other things both Napoleon and Wellington, and so they exist if it does. They’re both dead of course, but they still exist on the growing block conception because the past is equally as real as the present. That doesn’t seem absurd to me. What seems absurd is that we could add more events to the past and go on adding. It is absurd because, on the growing block conception, only the past and present are real and nothing else exists (or nothing temporal exists -maybe eternal and abstract kinds of thing may exist, but they’re a separate issue). But if nothing else exists, then where do all the new events come from? They must come from nothing, and nothing comes from nothing. So I don’t seem how a growing block conception of time can possibly be right. As it were, the growing block conception of time tells us there is so much reality on Monday and nothing else, and then tells us on Tuesday that there is more reality. But where did that extra stuff come from if there was nothing else?

This is what I mean by the conservation of reality. There can be no changes in the amount of reality. I think the intuition is perfectly symmetric and it is just as absurd to think of existent present and future events ceasing to be when they become past. Where does that reality go to? I just can’t imagine it.

Like I said, no one sees the force in this, but it has me enthralled.


13 thoughts on “Growing block, shrinking block, and the conservation of reality

  1. Much of traditional Christian theology would tend towards the B-series conception of time. Omniscience on the part of a divine being demands that the future be already known to that being. The concept of predestination led to a belief in the “elect” and all sorts of social and political corollaries.

  2. kenanddot

    Does omniscience demand that the future already exists? Surely if the future didn’t exist, it wouldn’t diminish God if he didn’t know it. On the other hand, maybe it’s part of the doctrine for other reasons that God knows what will happen to us in the future. And he can’t know it if it isn’t there.

  3. laura

    Ken: My worry is certainly more naive than your questions about the growing block model. I cannot work through any “model” of temporal reality that requires me to graph onto a hypothetical spatial object. It brings up conflicts for me like chilliagons must have for Descartes. Is there any other way to conceive of the reality of events over time that doesn’t require that each event (even metaphorically) either takes up space or disappears into nothingness?

  4. Ken,

    I was trying to ponder how Einstein’s “spacetime” might address your questions. If spacetime is the single fabric of the universe and if that universe is expanding, then would the growing block conception be more acceptable?

    (These thoughts do not come easily when one’s chief concern of the day has been slates missing from the church hall roof following last night’s storm)

  5. Ken,

    I was pondering your time question on the DART and suddenly remembered that at one point in a 1970s series of Doctor Who there was talk of a campaign for “real time”. Time lords kept going backwards and changing things to the extent that an entire civilisation had consequently disappeared from history.

    Doctor Who was clearly of the growing block school; it was possible to add to the past!

  6. ken

    I think philosophers would technically classify the Doctor Who scenario as a case of ‘world-hopping.’ World hopping occurs when you travel back in time and do something that changes, as opposed to influences or affects, the course of events. If you change the course of events, your life story continues in a divergent possible world peopled by mere counter-parts of the people you knew when your story began. But genuine time travel within the same possible world is possible, though still mysterious and paradoxical, if you merely go back in time to play the part it was always true that you would play then. If you don’t change the course of events, the past remains fixed, all that is required is that you played the role you played. The American philosopher David Lewis took this view.

  7. I guess a philosophical approach to these questions is going to be very different than a mathematical one… but it would seem to me that in this particular case, they need to overlap, or, rather, the philosophical must engage with the physical.

    Not being a philosopher, physicist or mathematician of any great standing, I can’t offer a complete answer joining the perspectives. But I think Laura’s objection to the use of geometrical symbols is far from naive. If time is seen not as a shape but as simply the movement or change of matter then the question of limited reality should be resolved? A point in time is merely a precise arrangement of matter in space that follows and is followed by a different arrangement of matter in space. There are no limitations to the possible arrangements of matter in infinite space so time is unending and reality is limitless. Time ends when the singularity is reached because when space is a point there is only one single arrangement of matter — and probably little room for variation on either side of the singularity.

    Maybe the past and future probably do not exist anyway. Past configurations do not really exist because they have already been altered. We can only imprint a tiny amount of any given point in time in our minds, in photos, in databases or books. These minimally complete texts themselves are undergoing change; if they are not stable how can their imprint of the past be? Future configurations, well, in a sense they may be said to exist because they are imprinted in the present configurations of the universe. If you could understand every physical law and every piece of matter then you could predict every future event. But just because a thing can be predicted does that mean it exists? Or does it only exist at the moment the prediction becomes true? Finally, it could be that even the does not exist because the movement of matter does not stop and the present cannot be isolated from any other time. By the time you have captured it, it is gone.

    I know I am probably missing a lot of valid philosophical points and mucking up the scientific ones, but it would seem to me that there is no time, only matter and change in matter that presents the illusion of time.

  8. Geoff

    It seems odd to say that the past exists. What we tend to say is that the past (or a past state of affairs) existed. Either a past state of affairs still exists and is therefore part of the present, or it has ceased to exist.

    Is there a convincing reason to think that past, and not present, states of affairs actually do exist?

  9. kenanddot

    Geoff said “Is there a convincing reason to think that past, and not present, states of affairs actually do exist?”

    I don’t know the area very well, so I can’t say. I think it is supposed to follow from the determinacy of truth of statements about the past (in contrast with statements about the future).

  10. Geoff

    Now that seems really odd to me…surely the truth about a state of affairs which once existed and may or may not now exist doesn’t imply anything about whether that state of affairs actually exists. Except if the truth is that it actually exists – but then it is a truth about a present state of affairs, not a merely past one.

    This seems so clear to me that I’m sure I’m missing something! Back to the textbooks for me I guess…

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