We’ll call this premise the causal premise or “CP” for short. In an argument featuring CP it will usually be other, more controversial premises that draw critical discussion. In the Kalam Cosmological Argument, it is more common to question the second premise’s claim that the universe began to exist than to question CP. Most critical discussion of Kalam centres on whether we really do have good scientific evidence or philosophical arguments for thinking that the universe has a finite history. But sometimes CP draws critical attention and is challenged too.
Sometimes it is asserted that, in fact, the recent findings of science have given us good reason to reject CP. It is alleged that research (usually regarding the quantum world) has actually shown us that some things (certain tiny particles) can come into being without any cause at all. When this assertion is made, what typically follows is a discussion of the particular research the challenger of CP has in mind, and whether it truly implies that some things have begun to exist without a cause. That’s all well and good but I think the question of whether science has refuted CP can be settled at a “meta” level. That is, when we reflect on the very nature of science, not just particular scientific endeavours, we see that science could never rationally lead us to conclude that CP is false. It’s just not within the possible scope of science to determine that anything has begun to exist without cause.
Why think science has such a limitation? Consider the state of affairs in science that, if obtained, would most suggest that CP is false. Presumably we would have some entity that we know is not eternal (we observe tokens of its kind beginning to exist) which we are trying to find the cause of. Let’s call this entity the appearing particle or “AP” for short. Presumably, if we’re tempted to say that AP is causeless, that’s because scientists are having a nauseatingly hard time locating a cause for AP. That is, presumably we have no plausible candidates for AP’s cause and almost zero confidence that we will find one. After all, if we had a plausible candidate for AP’s cause, or a reasonable hope of discovering one, we would likely not conclude that AP is causeless. To conclude that AP is causeless while a plausible causal explanation is on offer is to just throw away a potentially good explanation of AP’s existence. So, to reiterate, the most suggestive scenario for the conclusion that CP is false is the existence of something like AP and, after sufficient study of AP, a total lack of plausible causal candidates or hope for any to emerge.
How we interpret this scenario from here will depend on what we consider to be possible candidates to put on the table in a scientific explanation.
On quite a mainstream view of science, the discipline is constrained by methodological naturalism. That is, only naturalistic explanations can feature in scientific explanations. Only causes that are naturalistic are allowed in science. What exactly counts as naturalistic is fuzzy but taking a mainstream interpretation again, a cause counts as naturalistic if it is physical. So on this mainstream understanding of science, only physical explanations and causes can be appealed to.
Well then, assuming methodological naturalism in our above scenario, our scientists, in so far as they have been practising science and not something else (like pseudo-science), will have found themselves lacking any plausible physical cause for AP’s existence. They will have searched high and low for a physical cause for AP, come up short, and have good grounds for being highly sceptical of the future prospects of finding a physical cause for AP. This, given methodological naturalism, would be the scenario that would most suggest rejecting CP on the basis of science. But would we actually be rationally justified in concluding that CP is false on the basis of this state of affairs?
I think not. After all, because of methodological naturalism, none of the scientific research conducted will have examined the plausibility of a non-physical cause for AP. On methodological naturalism, non-physical causes just aren’t entertained as part of science. As such the scientists weren’t looking for non-physical causes and so wouldn’t have ruled out some such cause. So while the option is open to us to conclude that AP is simply without a cause, it is open to us to consider also that AP might have a non-physical cause. The question would then be: which is the more rational option to take?
It seems to me that it would always be more rational to conclude that AP has a non-physical cause rather than concluding that AP is causeless. If we conclude that AP is causeless we leave ourselves without any intelligible explanation as to why AP comes to exist exactly when it does, or why, if CP is false, it’s AP and not also tigers, cats, buildings etc that can come into being without cause. To make sense of what we observe we would need to suppose that there are some sort of rules that govern which non-existent entities can come into existence uncaused and when. But non-existence entities don’t exist! There are no rules that can apply to them. A non-physical cause, on the other hand, even if inaccessible to further study, could still in principle account for the order and intelligibility in APs coming to existence.
I conclude, then, that if we operate with methodological naturalism, the scientific scenario most suggestive of CP’s falsity would not in fact warrant the conclusion that CP is false. It would in fact strongly warrant the conclusion that there exists some non-physical entity! Of course, given the methodological naturalism, this conclusion – that AP has a non-physical cause - wouldn’t count as science. We couldn’t include it in a scientific textbook or teach it in a science classroom. But so what? It would still be what we should rationally believe. It would just fall under some other domain of human knowledge. Philosophy perhaps.
How do things look, though, if we instead jettison methodological naturalism as a constraint on science? What if, for the sake of argument, we allow scientists to entertain non-physical entities as well as physical entities as candidates for scientific explanation? What if any possible entity could in principle feature in a scientific account? Are the prospects for falsifying CP any better? Let’s consider such an unfettered scientific enterprise. What would be the scenario most suggestive of CP’s falsity?
Presumably it would be much the same as the previous scenario but with much wider scope. That is, our scientists are trying to explain how AP comes to exist and have no plausible candidates for explanation of any possible sort. There seem to be no physical entities or non-physical entities that work as a causal explanation of AP and it seems highly unlikely that any will emerge. Again, if we did have a plausible candidate, we would reach for it, and the scenario would not be suggestive of CP’s falsity. But we are imagining the scenario most suggestive of CP’s falsity and so we are imagining that no plausible cause is at hand. With physical causes and non-physical causes of AP utterly lacking, everything would seem to be ruled out. AP’s coming to exist would seem utterly causeless.
This looks like a more promising scenario for rationally concluding that AP is causeless. Trouble is, this scenario could not ever possibly occur. That’s because while we are throwing open the scientific gates to any conceivable entity, we are always faced with the following possibility: there exists an entity E that is the cause of AP but which is otherwise utterly imperceptible to scientific study. Such an entity could never be scientifically ruled out and is always a potential explanation of AP. Indeed, E would always be a better explanation of AP than that AP began to exist without cause, for the same reasons of intelligibility elaborated above. Even entity E allows, in principle, for the intelligibility of APs coming to exist in a way that the causeless explanation does not.
So even if the floodgates of science are opened way wider than methodological naturalism allows, the most suggestive scenario of CP’s falsity could never rationally warrant the belief that CP really is false. The most radical possible scenario would actually warrant the belief in an entity like E which explains AP but which we cannot otherwise scientifically study. And the conclusion that E exists would even be a proper part of science.
However you slice it, then, science just cannot directly rebut the causal premise.