Does Micro-indeterminism entail Macro-indeterminism?

A professor of mine, with whom I habitually disagree (much to his pretended ‘chagrin’ and our mutual amusement), has argued previously, and again recently, that even if indeterminism were true at the micro-level, for instance at the level of quantum mechanics, that would do nothing to make macro-determinism infeasible, where macro-determinism means something like: for every macro-physical event E, either (i) there is always exactly one macro-physical event E* from which E followed deterministically, or at least (ii) E, if it is not preceded by any physical events, deterministically entails all proceeding macro-physical events. I have previously expressed my skepticism about the thesis that if quantum indeterminacy were really true, then it would yield no consequences for the thesis of physical determinism on the macro (i.e., ‘observable’) level. It seemed to me that if quantum indeterminacy were really true, then it would always in principle be metaphysically and even nomologically possible for some macro-physical event of type E (which, with law-like regularity, causally brings about some subsequent macro-physical event type E*), to obtain without E* subsequently obtaining. To fail to recognize this, I thought, was just not to take quantum indeterminacy seriously. Even if the probability that macro-physical event E occurred without bringing it about that E* occurred is vanishingly small, so small as to be reputed practically impossible (say something in the order of, or less than, one chance in ten to the power of fifty, or something like that), it would still be physically possible for E to occur and E* not to occur. I argued that although there are some properties for which it is false to say ‘if one part of a whole has property P, then the whole has property P’ – for instance, if a song on an album has the property of being under three minutes long, it does not follow that the album has the property of being under three minutes long[1] – there are other properties for which it is true to say that ‘if one part of a whole has property P, then the whole has property P.’ For instance, suppose one part of a whole has the property of being extended in space; it does clearly follow from that that the whole has the property of being extended in space.[2] We call it a ‘fallacy’ because the inference from part-to-whole isn’t always and everywhere truth-preserving, but that doesn’t entail that it is never anywhere truth-preserving, and it is intuitively obvious that it is an inference immune to the problem of truth-preservation in at least some instances. Thus I argued that the property of being indeterminate was one of these instances, so that if some part of a whole (say, where the ‘whole’ is the continuous space-time, and the part in question is the quantum foam) has the property of being indeterminate, then the whole has the property of being indeterminate.

However, more recently I had been considering revising my view, and in trying to revise it I had to think through some of the considerations which I want to explore in this article. I will, here, lay out a case for defending my professor’s contention, and then subsequently argue that while I can imagine a possible world in which micro-indeterminism and macro-determinism were both true, such a world is not part of the set of physically possible worlds. What has to be denied, in order to reconcile micro-indeterminism and macro-determinism is, I think, too much.

First, the case in defense of the thesis that micro-indeterminism does not entail macro-indeterminism could go something like this: there is some finite set of possible and indeterminate quantum mechanical events [Q1, Q2,… Qn], and nothing determines which of these events will occur. This is sufficient for micro-indeterminism. Now suppose that each member of the set [Q1, Q2,… Qn] would either (i) (along with the set of macro-physical events preceding it) bring some macro-physical event P about necessarily, or else (ii) at least would do nothing to impede P’s coming about deterministically from some set of antecedent macro-physical events. So, on the first story Q1 ⊃ P, and Q2 ⊃ P, and so on, so that (Q1 v Q2 v … Qn) ⊃ P. On the second story there is causal closure of the macro and/or micro physical levels, so that each of these levels is entirely causally autonomous from the other. If either of these two stories worked, then one could safeguard macro-determinism even while conceding micro-indeterminism.

Do either of these stories work? I was, for a time, tempted to think that the first one could work in principle. After all, it seemed logically possible. The second is a little more queer because it is hard to imagine that micro-physical events could be called genuinely ‘physical’ events if they were not in any sense causally connected to the observable physical realm – what would it mean to call them ‘physical’ if they were not part of one single physical plenum? However, maybe the second story deserves more sympathy than that. Perhaps the word ‘physical’ has a wider use, so that we can even refer to universes in a multiverse ensemble (if such an ensemble exists) as physical, and the events occurring in them would be genuinely physical events, even if they were causally sealed off from our observable physical world. However, something is obviously wrong, in fact, with both of these stories, as I intend now to illustrate.

Suppose that there is a macro-physical brain-state event B1 which is caused by some ‘observation’ of an (indeterministic) quantum mechanical event (of course this wouldn’t be direct observation, but just suppose that all the appearances where such that, given my scientific paradigm, it appears to me that some quantum mechanical indeterminate micro-physical event has occurred – i.e., I can ‘detect’ it). Suppose that the set of all macro-physical events prior to B1 is symbolized by ‘S’, where each event in S is either entailed by all the events prior to it, or at least, if there is a ‘first event’ in the set, that it will entail all of the events subsequent to it in the set. Let this world with S & B1 be symbolized as W. Now, there is a logically possible world W’ which is maximally ‘close’ or ‘near’ to W, in which S obtains, but B1 does not obtain. Instead, S obtains along with B2, where B2 is the observation of a different quantum mechanical event (or none at all). Here, since both B1 and B2 are macro-physical events (i.e., observable brain states), it seems as though micro-indeterminism has led to macro-indeterminism. Notice that our logically possible worlds (W: [S&B1], and W’:[S&B2]) are both metaphysically possible, and nomologically possible given our currently best understanding of physics (at least to the best of my knowledge, and accepting for the sake of argument that an indeterministic model of quantum mechanics is correct insofar as it is indeterministic).

Consider the fact that observable brain states can be caused by (indeterministic) quantum mechanical events – if this is true, then neither of the stories we told work in fact. Quantum mechanical events, if they are really indeterminate, and if they really can, under certain conditions, cause different brain-states to actualize, and the actualization of brain-states is a macro-physical event, then clearly micro-indeterminism of the kind attested to in the standard Copenhagen view of quantum mechanics really can (and necessarily can) bring about some macro-physical observable event which would otherwise mutatis mutandis not have occurred. (I should add here a quick caveat lector: I do not endorse or believe in indeterminism of this kind, I mean only to accept that there is such indeterminism for the sake of argument – to see what would follow). For either story to work, we need micro-physical indeterminacy to be in principle undetectable to science. So, we can conclude that if detectable micro-physical indeterminacy exists, then micro-indeterminacy does entail macro-indeterminacy. In other words: detectable micro-indeterminacy entails macro-indeterminacy. Even in a world where micro-indeterminism were true and macro-determinism were never observationally disconfirmed, macro-determinism would, given ‘detectable’ micro-indeterminism, not in fact be true.

This same conclusion could be derived if we accepted the doctrine of mereological supervenience, according to which, as Jaegwon Kim explains, “[the] properties of wholes are fixed by the properties and relations that characterize their parts.”[3] If the set of properties and relations which characterize the physical world at the most basic level include indeterminacy then it seems to follow from mereological supervenience that the properties of the observable physical world include indeterminacy, even if nothing we bear witness to on the observable level would lead us to suspect its indeterminacy.

The intuition of my professor, I assume, is something like this: whatever happens at the quantum level, if we suspend an 18-wheeler 30 feet off the ground and then let it go, it will fall; come what may on the quantum mechanical level, that 18 wheeler is necessarily going to fall to the ground. Is this true? I’m not sure. I can imagine a set of quantum mechanical events all conjunctively occurring (however unlikely) such that the truck just disappeared, but this might just be my failure to distinguish science from science fiction.

Macro-physical determinism (Macro-determinism for short) is true if and only if every single macro-physical event either follows deterministically from others, or else at least deterministically entails all successive macro-physical events. If micro-physical events are indeterministic and observable or detectable by creatures whose brain-states are macro-physical, then macro-determinism is false. Even in a world where there are no observers at all, if there are indeterministic events which, counterfactually, would be observable were an observer appropriately situated, then that world is (macro-)indeterministic. The difference between the micro- and the macro- physical, after all, is purely anthropomorphic. There just is, in reality, no causal separation between events which are not observable to us, given the human organism as, in the words of Bas C. van Fraassen, “a certain kind of measuring apparatus,”[4] and those events which are observable to us. Our being organisms for whom some physical events are directly observable, and for whom others are merely detectable, does not give us any reason at all to think that unobservable physical events have no causal efficacy for bringing about macro-physical events. The atomic bomb is evidence enough of that. The idea is that the world really is a causal plenum. Imagine, by analogy, that each event in the physical world hooks up to all other physical events so as to make the whole aggregate different then it otherwise would have been without it, in the same way that the meaning holist thinks that each belief in a web of beliefs determines the character of all of the beliefs in that particular web.

This seems to settle the case pretty definitively, since a difference in the brain states of some observer can plausibly bring about a very different causal chain of macro-physical events. Thus, even if there is a logically possible world in which both micro-indeterminism and macro-determinism are true, it certainly isn’t our world, nor any worlds near enough to ours where there are detectable indeterministic events of any kind.

Is there a way out of this? Perhaps; for one thing, all somebody needs in order to claim that micro-indeterminism does not entail macro-indeterminism is that there be some logically/metaphysically possible world in which micro-indeterminism and macro-determinism are both true. I can imagine somebody arguing that when an observer ‘observes’ (mediately) a quantum mechanical event, the observer determines (by observing) what would otherwise have been an indeterminate event. Here the suggestion is that observation has the effect of making a macro-physical event deterministically cause a micro-physical event, but that no unobserved micro-physical events ever bring about a different macro-physical event. Is this possible? We are putting to one side the question of whether this gets the science right (I make no pretensions to understand the dynamics of quantum theory, since I am a philosopher and adamantly not a physicist); the question is rather ‘if this did get the science right, if this were really how the world were, then would it follow that micro-indeterminism could be conjoined with macro-determinism?

This would have to deny Heisenberg’s uncertainty principle, the cornerstone of chaos theory (which, contrary to folk-science, is actually a deterministic theory). The intuition behind chaos theory in general is just that every event, no matter how seemingly insignificant, has an impact on the whole causally-continuous world. A butterfly flaps it’s wings twice, as opposed to once, within some finite span of time, in central park, and a hurricane is set to hit the shore of Australia where it otherwise (keeping all else besides the extra butterfly-wing-flap the same) would not have. However, that’s no surprise – after all, chaos theory is built on the assumption that the world is a causal plenum, and this is perhaps the very thing being denied. If one is sincere in her commitment to the indifference micro-indeterminism makes for macro-(in)determinism then it seems there has to be causal closure of the micro-indeterminate level, such that no micro-physical event can even in principle bring about an observational difference, which would mean that no indeterminism could, in principle, be observed. If it were observed, (at least if it were observed by physical creatures whose brain states could be observed) then by that very fact it would have caused a macro-physical event.

It would have to be that the micro- and macro- levels were causally sealed off from each other, or causally indifferent to each other; at least that either the indeterminacy of the one was causally impotent with respect to the other, or that the determinacy of one was causally indifferent to the indeterminacy of the other. To be truly indifferent, though, the indeterminacies would have to be in principle unobservable – or at least they could not be observable/detectable in principle by beings whose observational apparatus was significantly physical. This, however, raises a troubling conundrum for the philosophy of science. Since the range or set of nomologically possible worlds is determined by our best scientific theories, and since those are birthed by methodologically empirical observation, it seems odd, and perhaps even incoherent full stop, to say that there is a nomologically possible world where physical events occur in such a way that they could not, in principle be detected or figure into our theories born of empirical observation. Perhaps there is a metaphysically possible world where materialism/physicalism is correct, and this case-scenario obtains, but it would not be a nomologically possible world. In fact, it seems a necessary truth that such a world would not be nomologically possible!

Is it metaphysically possible to have a causal quarantine of the micro-physical indeterminate level? If it is, then micro-indeterminism does not strictly entail macro-indeterminism. Moreover if that kind of quarantine is possible, then why not a quarantine of a certain set of macro-physical events? Maybe there are some macro-physical events which are deterministic in the sense that they will follow each other ‘come what may’ elsewhere (even come what brain-state events may). For instance, if the universe is expanding at escape velocity and thus faces imminent heat-death, then (plausibly) no combination of quantum mechanical events (or macro-physical brain-state events), however unlikely, will steer the universe clear of this apocalyptic course. This kind of macro-determinacy would be weaker than the macro-determinacy we have had in mind (pace the definition I offered above), but it would still be some kind of macro-determinism.

Therefore, micro-indeterminism nomologically entails macro-indeterminism just in case both (i) micro-indeterminism is observable in principle by creatures whose brain-states are macro-physical, and (ii) no set of macro-physical events is causally quarantined from the rest of the macro-physical order. The cost of denying (ii) is no less than the presumption that the world is a causal plenum (an assumption upon which some of our scientific theories, like Chaos theory, are built), along with mereological supervenience. The cost of denying (i) is to abandon the view that the range of nomologically possible worlds is set by what would be in principle empirically verifiable by observers situated appropriately/idyllically  in the logically possible world in question. Maybe this second option isn’t as bad as it looks; perhaps we can imagine, given our best science, a logically possible world within the range of nomologically possible worlds set by our best science, where the same regularities held in fact, and where we would only ever and always observe (even in principle, we could only ever and always observe) phenomena which would proscribe the construction of our best scientific model(s). Whether it is coherent to talk about nomologically possible worlds where no observers idyllically situated could in principle, using the scientific method, come to apprehend the nomic regularities which held in fact is an issue which I will leave for further exploration another time, when/if I decide to dig deeper into the relationship of modal discourse and the philosophy of science.

To recapitulate, so far I have argued that the ‘fallacy of composition’ objection against inferring macro-indeterminism from micro-indeterminism doesn’t seem to work, just as it doesn’t work to object that way to the inference from some thing’s part being extended in space to the thing as a whole being extended in space (note that having the property of being extended in space as a whole does not imply that there is nothing more to a thing than it’s spacial extension). This argument is tenuous though, as it will rely in part on one’s intuitions, and could in principle be defeated given a better understanding of the science involved. I argued that the cost of denying the legitimacy of this inference would be (no less than) the doctrine of mereological supervenience, and the doctrine that the physical world is a causal continuum from top to bottom. I also argued that there cannot in principle be a nomologically possible world were observers with a physical apparatus could not in principle detect indeterminacy if indeterminacy were a nomic reality. This is because it seems to me that to say that something is undetectable to physical science in principle is plausibly just to say that it is not physical. I have also conceded, however, that perhaps there is a more modest form of macro-determinism, call it weak macro-determinism, according to which there is some subset of macro-physical events which follow deterministically from each other come what may elsewhere. The universe’s facing heat death is one example of something which, come what brain-states may, seems physically inevitable. This, however, is not strong enough for macro-determinism as such, and thus has nothing, or in any case very little, to do with the present discussion. If observers can in principle stand in a ‘detecting’ relation to nomic indeterminacy (whether of the macro or micro variety), then macro-indeterminism follows of nomological necessity.


[1] I am here adapting an example I first read here: Is The Universe Contingent? (

[2] I gave this example previously on my Undergraduate Blog, in an article called: The Fallacy of “The Fallacy of Composition” Objection (

[3] Jaegwon Kim, Mind in a physical world: An essay on the mind-body problem and mental causation. (MIT press, 2000), 18.

[4] Bas. C. van Fraassen, “Empiricism and Scientific Realism” in Philosophy of science: The central issues. Second Edition, edited by Curd, Martin, and Jan A. Cover. (WW Norton, 1998): 1070.


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