Are there different possible outcomes of the future? Or phrased more broadly: do ontological possibilities exist? I think this is a profound question, and one may think much depends on our answer to it. For instance, if ‘ought’ truly implies ‘can’, and the only real ‘can’ there is is whatever in fact happens, it would seem to follow that the only thing that could ‘ought to happen’ is what in fact happens.
Ontological possibilities here stand in opposition to what we may call hypothetical, or ex-ante possibilities. That is, we are clearly able to think in terms of different outcomes being possible, and to then plan and take action based on such thinking, but that does not imply that those outcomes were ever genuine possibilities in a deep ontological sense.
Worth noting is it that there seems to be a contradiction between two widely shared views that pertain to the existence of ontological possibilities. For on the one hand we have what appears a widely accepted distinction between necessary and contingent truths, necessary truths being ones that must be true because negating them would imply a contradiction with reality (commonly cited examples are 2+2=4 and syllogisms), while a contingent truth is one that could have been false, as its negation (supposedly) does not imply a contradiction with reality (e.g. “Life evolved on Earth”, “Hillary Clinton lost the 2016 election”).
Yet this does not seem consistent with another prevailing belief, namely that the entire world unfolds according to deterministic mathematical equations. If the latter is true, then any truth about the world would appear a necessary one, as its negation indeed would imply a contradiction with the fundamental equation(s) just as much as does 2+2=5.
So what are we to make of this? What could possibly be true about ontological possibilities?
Why Ask This Question?
My reason for examining this question here has to do with ethics – more specifically, it has to do with an objection one might be tempted to level against the sensibility and meaningfulness of ethics. For, in light of the ought-implies-can note above, one might claim that ontological possibilities are necessary in order for ethics proper to get off the ground, and indeed for engagement in ethical reasoning, decision-making, and action of any kind to even make sense.1 A combustible and controversial claim for sure. Yet I shall entertain no discussion of it here.
Instead, my aim here is to argue that if one thinks ontological possibilities are required for “the meaningfulness of ethics” – i.e. required in order for engagement in ethical reasoning, decision-making, and action to make sense – then one cannot reasonably reject such “meaningfulness” with the claim that ontological possibilities are not real. The reason being, in short, that we simply do not know whether such possibilities are real or not, and, as far as I can tell, we all but surely never will.
The Nature of the World: Does Quantum Mechanics Preclude – or Describe – Ontological Possibilities?
In order to say whether ontological possibilities exist, it seems apt to look toward what is arguably our most fundamental and well-tested theory of the world, namely quantum mechanics, and see what it has to say about it.
The answer is that it depends on which interpretation of quantum mechanics is correct, a matter concerning which there is much disagreement among experts. And in light of such disagreement, it only seems reasonable to maintain a substantial degree of uncertainty concerning which interpretation is correct.
As for how one should break this uncertainty down more specifically, there seems plenty of room for reasonable disagreement. For instance, assuming the formalism of quantum mechanics indeed does describe the world in the first place, it seems defensible to place 50 percent probability on the claim that none of the well-known interpretations are correct, and to distribute the remaining 50 percent of one’s credence among the (more or less) mainstream interpretations. This could then be done based on how many subscribers these respective interpretations have among experts, in which case it seems one should assign roughly equal credence to the so-called Many Worlds Interpretation and the Copenhagen Interpretation – perhaps 20 percent to each – while distributing the remaining 10 percent to the remaining ~10 interpretations, resulting in about one percent credence in each of them.
That would be one way one could do it. I don’t necessarily agree with the exact numbers in this distribution; it is just an example that seems within the bounds of defensibility. What does not seem defensible, however, is to maintain complete certainty in the veracity of any one particular interpretation. And this is true for various reasons. For not only are there many competing interpretations that all seem to have at least some strengths and weaknesses, and not only can the possibility that the correct interpretation is a yet unformulated interpretation not be ruled out; the possibility that no interpretation of the formalism is true also seems a very open one.
After all, we have seen it happen before that a prominent physicist considered the, admittedly impressive, canon of physics of his time complete but for a couple of anomalies, only for those anomalies to then revolutionize physics completely within a few years. How can we maintain near-complete confidence that the same could not happen with the physics of our time? Indeed, who is to say that quantum mechanics isn’t still just one of the outer layers of the onion, no less a parochial approximation of the underlying dynamics of reality than classical mechanics ultimately?
Where does all this leave us with respect to ontological possibilities? It leaves us with substantial uncertainty. In particular, it leaves us uncertain about whether the world unfolds according to deterministic mathematical equations or not. Out of the 14 (at the time of writing) established interpretations of quantum mechanics listed on this Wikipedia page, only four are deterministic, seven are indeterministic, while three are agnostic. Consequently, although the deterministic interpretations include the relatively popular Many Worlds Interpretation in which all the mathematically possible outcomes of the formalism are realized, it seems overconfident to have anything near complete certainty that the right interpretation, to the extent there is one, is deterministic.
Indeed, among the 14 interpretation cited above, one of them, the transactional interpretation, is, at least as its proponent Ruth Kastner defends it, explicitly realist about ontological possibilities – a “Many Possibilities Interpretation”, if you will.2 Thus, according to this interpretation, the mathematical formalism of quantum mechanics is in fact the mathematics of ontological possibilities (apropos, perhaps also see possibility theory).
Now, my purpose here is not to settle which interpretation that is most plausible, much less which one is correct, but simply to argue that near-total confidence in the truth of deterministic interpretations is not defensible. On the rough sketch of a credence breakdown above, for instance, the transactional interpretation was given about one percent probability, and I don’t think one can defend giving it several orders of magnitude less than that. And even if one could, there are still other indeterministic interpretations that also deserve at least some weight, as well as a big space of “yet unknown interpretations that could be true” – what was assigned a 50 percent probability above – of which a substantial chunk should be expected to consist of indeterministic interpretations.
Combining these considerations, it seems overconfident to maintain a 99 percent credence in the proposition that the right interpretation of quantum mechanics is deterministic, and the same can reasonably be said, I believe, of any such credence above 95 percent as well.3
One could, of course, argue for uncertainty about this question through other routes as well, such as by invoking the idea that we always should maintain at least some degree of doubt, however minute, about any claim (an idea I have defended here), or the related claim that our entire conception of reality – not merely our physics – might be wrong, or perhaps not even that. Yet, as the argument above should make clear, one need not resort to these claims in order to reach the conclusion that it is reasonable to have a non-trivial degree of uncertainty regarding the matter of determinism and ontological possibilities.
[Another case for the existence of ontological possibilities, a case not made at the quantum level, is Helen Steward’s argument for the reality of “agential settling”, which she has presented in the book A Metaphysics for Freedom. Thus, one can be forced to increase one’s credence in the existence of ontological possibilities further by assigning a small credence to this position as well.]
Implications for (Objections Against) the Meaningfulness of Ethics
The conclusion above means that, if ontological possibilities are required for “the meaningfulness of ethics” – the conditional assumption that was our point of departure – the uncertainty we should maintain concerning the reality of such possibilities means that a rejection of ethics on the basis that ontological possibilities do not exist is unwarranted.
To be sure, one may reasonably argue that, if ontological possibilities are required for “the meaningfulness of ethics”, then it seems likely that no such meaningfulness exists. Yet that is a far cry from a refutation of such meaningfulness. For consider by analogy the claim that risks of terrible future outcomes are low, and hence that such outcomes most likely will not be realized. Even if such a claim were true, it by no means follows that such risks can reasonably be dismissed.
When the stakes are sufficiently high, it is not reasonable to dismiss low probabilities. And when we are discussing the meaningfulness of ethics, it seems that the stakes could not possibly be greater, as the subject in question comes down to whether there are any stakes at all. In light of such stakes, even extremely low probabilities should be taken seriously; and yet the level of uncertainty we found reasonable to maintain concerning ontological possibilities was not extremely low, much less Pascallian by any stretch.4 Thus, if ontological possibilities are required for the meaningfulness of ethics, the epistemic possibility of the reality of such ontological possibilities should be taken very seriously indeed.
Moreover, when considering the outcomes of the options before us, an emerging asymmetry appears to make the choice clear. For if ontological possibilities are real, and ethical action amounts to trying to realize the best of these possibilities – to create the best ontologically possible world, if you will, or at the very least avoid the worst ones – it would seem that we have good reason to try to act accordingly, and no compelling reason not to. If, on the other hand, ontological possibilities are not real, trying to realize the best possible world appears to have no cost. We thus seem to have a strong reason in favor of trying to create a better world, and no reason against it.
Lastly, if we entertain the negation of the assumption that served as our starting point, namely that ontological possibilities are not required for the meaningfulness of ethics – again without saying whether this claim is true or not – we appear to arrive at the same conclusion: we have no reason to consider ethics meaningless or to not try our best. In conclusion, no matter our starting point, the meaningfulness of ethics seems on firm ground.
1. Alternatively, I could also say “the meaningfulness of trying to improve the world” or of “trying to improve one’s own situation.” These things ultimately all mean the same in my view, cf. You Are Them. Yet even if one considers these statements different, the argument I make here still applies equally to them all. That is, one can readily swap, say, “the meaningfulness of ethics” with “the meaningfulness of trying to improve one’s own situation”, and the argument would run just the same.
2. Although it should be noted that other indeterministic interpretations also hold ontological possibilities to be real, at least implicitly.
3. I have not discussed eternalism here, which is a deterministic view, but suffice it to say that, at the very least, one ought to maintain substantial doubt on this matter as well, one reason being that the mere fact that the physical equations do not appear to require an ontologically real present does not, contrary to what seems widely believed, imply that there is no ontologically real present. Much confusion about this issue seems to emerge from the belief that “ontological present” must mean “all clocks show the same”; presentism in that sense is surely as dead as can be, but presentism in general is not – there is no contradiction whatsoever about an ontologically real present in which there are (initially synchronized) clocks that show different times.
Beyond that, to turn the tables a bit, one might also ask why someone who holds an eternalist view would act to influence the future rather than the past, given that past and future both already exist on this view. It seems to me that eternalists are aligned with common sense rather than their own view of time in this respect. Also, to what extent does it make sense to say that all moments exist “always”? After all, doesn’t “always” refer to something occurring over time? The meaning of claims of the sort that “every moment exists always” is, I believe, less obvious than proponents of eternalism appear to think, and seems in need of unpacking.
But once again, the main point I wish to drive home here is not that people should consider presentism most plausible, but merely that we should maintain substantial uncertainty concerning this question as well.
4. What might perhaps be considered Pascallian, or at least more so, is the proposition that we are living in the multiverse described by the Many-Worlds Interpretation and that ontological possibilities exist within this multiverse. Yet in this case the stakes appear to become more than great enough to justify even Pascallian probabilities. Hence, this possibility appears worth taking seriously as well.