Scientifically we cannot know. But that doesn’t mean we cannot know that the general existence of change requires a cause. We can know because we know that the alternative is impossible. Change cannot come from nothing (change understood as necessarily involving an actualisation of potential). We can judge that physical reality is essentially a natural progression of possible states, and therefore we can judge that it’s cause is not essentially a physical being. This knowledge however has nothing to do with the scientific question of what came before the big-bang. For all we know our universe is one among many, a potentially infinite group of beings which in turn could have proceeded from the transformation of some other physical nature. But in any case we are still dealing with something that is in a continuous state of transformation or change.
The bottom-line is that such a nature, regardless of what form it takes, is not a self-existing self-explanatory act of existence precisely because it is a progression of possibilities rather than something that just exists. That’s why we argue for the existence of an uncaused-cause or an ultimate reality, not in a physical sense, but in an existential sense, and it is necessary because physical reality could not exist otherwise. And the laws of physics could not exist unless something determines how it works and that would require an intelligence.