Re-running The Universe: Determinism, Indeterminism, Quantum Stuff

[This is part of a set: Thinking]

The philosophical persuasiveness or either determinism or indeterminism has been made foggy by the success of quantum physics, in particular the apparent indeterminate nature of the world, that is the result of quantum physics.

One question that arises is the extent to which we can be sure, or not, that the universe is deterministic. Does ontological determinism hold?

[This follows from another post which assumed determinism for the points made. It ignored quantum stuff.]

From the point of view of a scientist there is the laudable position that we go wherever the evidence leads – and I agree with that. It appears that all the science is telling us that we live in a quantum indeterministic world, but with determinism at the macro level that allows us to make limited predictions.

So, if anyone wants to argue on the basis of evidence, then that’s it. The world is a deterministic+indeterministic mix. But it is indeterminate anyway, epistemologically, to those entities within it.

At our macro level we can still argue that there is a determinism that appears as a result of any quantum event, once it has occurred. Once a particle has had a causal effect on another, to a measurable degree, then the outcome is, within limits, deterministic.

One question that often arises is this. If we ran the universe again, would all the same events occur? The quantum non-determinist would say that, no, it would not, because quantum events are by nature indeterminate and would result in a different outcome.

But, given that we can’t re-run the universe this is a speculative position. Here I give several alternatives that I see. What follows assumes there is some sort of existence of something outside our universe – that our universe is contained in some way, so that the starting conditions can be set up the same way, down to whatever detail one might like to speculate about.

Determinism seems to require causality, otherwise what does it mean for one state to be determined by prior states. On the other hand, if there is a genuine time symmetry, then effects would cause causes, when considering time reversal. A one-way time dimension can also be causal the one way (which is what we perceive), and yet even in this universe Galilean physics is time reversible. Anyway, putting time issues to one side for now, here we go:

1) Indeterminate Universe. In this case there might or might not be causal relationships. It might be the case that there is no causality, just correlation – weak observed correlation. How does a completely indeterminate universe allow for predictability? Maybe it doesn’t. Maybe what we perceive as repeatable predictable outcomes – say from y = mx + c – are just coincidental correlations. If the universe is so indeterminate in actuality, in practice it’s difficult for us to figure that out, to ‘determine’ its indeterminism, as it were. This is somewhat like the reality-solipsism dilemma – we can’t tell the difference. The point though, in the context of this post, is that to re-run this universe with the same starting conditions will result in a different universe each time.

2) Deterministic Universe. In such a universe every event is determined causally by prior events. This is a point of view that might have been held prior to our discovery of the quantum indeterministic nature of the universe. In such a universe it would re-run exactly as it did on a previous run. On the face of it, at the macro level, it seems a reasonable working hypothesis. We observe what we think are deterministic connections on many levels of science, and other than quantum indeterminacy, we’ve observed no evidence against determinism.

3) Quantum Indeterminate Universe. In such a universe, even with identical starting conditions, the re-run would produce a different universe, because of the truly indeterministic nature of quantum events. This seems to be how some scientists view the consequences of quantum physics in our particular universe. But this seems to require some knowledge of facts outside our scope. Consider, if the quantum indeterminacy is, at some other level, actually determinate, but our understanding of physics is mistaken, then how would we tell the difference? Only a re-run of this universe would reveal the true quantum indeterminacy because a different universe would appear on each run.

4) Quantum Determinate Universe. In this universe even the quantum events are determined – though I refuse to speculate on how that might occur. Note though, that to the entities contained within each ‘run’ of that universe the quantum events would still be non-deterministic, because those entities are contained within the re-running universe and are bound by the evolving quantum events that are taking place. So, on each re-run, the inhabitants of the universe are convinced that their universe is non-determinate because of the observed quantum events, and yet on each re-run the very same quantum events are occurring, deterministically, and each re-run produces an identical universe.

Now, (4) is purely speculative of course. But then so are all of these options, because we don’t have a view of our universe from the outside and over re-runs of it. So, I don’t see any justification for being dogmatically committed to any of these views.

Perhaps the important point is that we do not know what our science is telling us about the deep status of our universe. It is all metaphysical speculation. And, I repeat an earlier point, to us it’s all indeterminate anyway. We cannot tell the difference between a determinate and an indeterminate universe if we ar a part of it.

7 thoughts on “Re-running The Universe: Determinism, Indeterminism, Quantum Stuff

  1. I don’t think there we could ever be sure about determinism. The most basic problem is that we don’t have the opportunity to “rewind the tape” and compare results.

  2. Hi Neil,

    Agreed. But we can’t seem to escape causality – it’s the very basis upon which we think about things happening. Even with what we think are truly random events, we may not know their source, but we do observe the effects they appear to cause, that they determine. Event the Schrödinger’s cat thought experiment has just one completely indeterminate event that is supposed to unfold only when ‘observed’, but everything else in that thought experiment is thought to be deterministic.

    This is why, elsewhere, I use determinism as a sufficient approximation to what’s going on. It’s a convenient model.

    But, like Laplace, I don’t expect anyone to actually do anything like full-system deterministic calculations. We don’t have access to an external demon with the capacity. Ontological determinism, epistemological indeterminism. Whenever we need to, when considering quantum effects, we can always use the ontological+epistemological indeterminism. As we often do, use different models when it’s convenient.

  3. Many people take the view that quantum indeterminism is a micro-effect, but that it does not effect macro events (large scale events). And therefore we can ignore it and assume determinism. However, there are research papers published on quantum randomness. And, in my book, the publication of a research paper is a macro event. So people do seem to be able to act in ways that amplify quantum events so that they result in apparently undetermined events at a larger level.

    Of course, this does not rule the possibility that everything is still determined anyway, in some manner that is unknown to us.

  4. “…there are research papers published on quantum randomness. And, in my book, the publication of a research paper is a macro event.”

    To clarify, you’re saying that random quantum events, by virtue of the fact that they are observed, so causing an observer to have a change of brain state with regard to quantum events, on through a chain of causal events, eventually cause a macro paper to be published? Good point.

  5. I like your approach on “physicalism” being precisely that desired explanation (the one which those who refuse physicalism claim we need instead) and your whole approach (duality of descriptions, e.g. solipcism indistinguishable from other descriptions). However, here you show how the naive-realist roots of physicalism lead you astray. That we must (in some sense) assume an “outside reality” is one thing, but you assume the existence of that reality in such a way that it seems meaningful to talk as if some god could run it several times, and thus you fail here almost miserably (relatively speaking, considering that you well avoid similar mistakes in the other posts I read).
    You write:”because we don’t have a view of our universe from the outside and over re-runs of it. So, I don’t see any justification for being dogmatically committed to any of these views.”
    Similar to the solipsist being forced to define a physical world in order to describe her dream, the fact of that there stricktly is no “outside” to totality (the fundamental *uni*verse) means that you should be committed to the consequences of that for making sense in your description, say on what probability means. Sure, given your other writings, the meaning of “apparent indeterminism” as a sort of illusion should be fruitful with you. 😉

    1. Hi Sascha,

      Welcome, and thanks for commenting.

      “… you assume the existence of that reality in such a way that it seems meaningful to talk as if some god could run it several times, and thus you fail here almost miserably”

      My use of the outside view is only a rhetorical tool, a thought experiment, used to explain the unfortuneate position we are in with regard to determinism/indeterminism. I’m not assuming it in any.

      However, though my use of an ‘outside’ in this case is merely a tool I don’t know exactly that there is no such ‘outside’, any more than I know there is one. I don’t know what the “fundamental *uni*verse” is in order to say whether the term ‘outside’ is meaningful. I don’t know if it is meaningful to speak of our particular universe as one of many, one contained in someway within one or more others, or coincident with others, or related sequentially in time, or even if ‘time’ has any meaning in that sense.

      My ignorance in all this is all I can vouch for. So I’m not sure what you think I’m committing myself to (I think very little) or what you think I should commit myself to. So I’m not really sure what you are getting at with …

      “the fact of that there stricktly is no “outside” to totality (the fundamental *uni*verse) means that you should be committed to the consequences of that for making sense in your description, say on what probability means.”

      I can, in the mean time, try to say what I think probability means.

      First I distinguish: probability, statistics, (pure) randomness.

      Probability is a predictive tool we use that takes what we learn from statistical observations about the way the world works and form a mathematical model that best matches that. So, in tossing a coin we speculate that our 50/50 probability is a measure of the likelihood of heads/tails over many trials. Using axioms of mathematics (which we have yet to justify but which seem to be helpful) we label our models as ‘rules’ or ‘laws’ and become quite reliant on them.

      We suspect there might not be ‘(pure) randomness’ (the really interesting concept) because we think the coin outcome could be predicted determinsitically, if we could pay enough attention to the detail; but then we wonder if that is really the case because quantum stuff makes that seem less likely, if we have understood quantum stuff correctly.

      I don’t know any more than that. And as I said, the really intersting concept, of which I know nothing, is (pure) randomness. My use of parenthetic ‘pure’ is to distinguish randomness from statistical uncertainty, but only because I suspect there is such a distinction.

      I’d welcome more comments on this. Have I understood your criticism?

      I’ll also spend some time looking at your posts. I’m particularly interested in what you have to say on John Wheeler. Though highly speculative the concept of digital physics (and Floridi’s information) seems intersting. I’m trying to put together a post on knowledge as information that doesn’t require any commitment to traditional philsoophical definitions of knowledge; and which also leads on to how humans acquire/attribute ‘meaning’ to knowledge; so maybe your stuff will help there.

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