I think there’s a tricky thing about answering this question that most people never consider. “Cause” may not be as simple as a binary “it was caused” versus “it was not caused.” There may be a plethora of relationships or sources in the universe/in existence that are like cause, or like what we think of how cause works, but not exactly it.

Our notion of causality is (a) 100% mechanistic; (b) 100% deterministic (to clarify, science doesn’t necessarily regard the universe as deterministic since the advent of quantum physics, but we tend to only regard events as being caused or causal to the degree to which they’re deterministic, while the rest is just “meaningless randomness”); (c) physical; (d) linear in time; (e) strictly a progression of time advanced by the same absolute, immutable set of laws; etc.

So, that’s a lot of constraints, and it’s possible that there are modalities of “causality” that satisfy some of those constraints and not others. Those possibilities are just rather hard to wrap our heads around, maybe because they’re different from what we observe in our everyday, macroscopic, non-relativistic, biological-perceptual, physically incarnate lives, or maybe because the success of science and technology has culturally entrained us to be scientistic, physicalist, mechanicalistic and entirely left-brain dominant.

For example, one possibility for this kind of causality-adjacent relationship may be found in science itself, or at least philosophy. We observe that the nature of this physical universe is just right for life to come into existence. If the fine structure constant were just a fraction of a percentage different, for example, matter and thus life would be impossible. So, we say that maybe there’s a multiverse, and every possible reality with every possible physical set of laws manifests “somewhere,” and this is just one of the ones in which life is possible to come about and hence to ask, “why is the universe suited perfectly for life?”. And physical theories themselves such as MWI and string theory tend to lead to such a conclusion, too, albeit without any direct evidence.

But the thing is, the big bang is thought by many to be the beginning of time itself. Or not exactly a “beginning,” but that time “curves around” at the big bang in higher-dimensional space in a way analogous to how the Earth’s surface curves around so that you can travel around it forever even though the earth itself isn’t extended infinitely in 3D space. So how, then, could the multiverse, or the principle of creation of universes, have created, or caused, this particular universe? It must have been done in some way that stands outside of time, or outside of time as we know it. This obviously violates a number of implicit constraints placed on our typical notion of causality, if not all of them.

Another such possibility is that God created the universe, or that maybe it was some spiritual being that’s enormous and advanced but not quite (directly) God. What is spiritual “causation” like? Who can imagine!?