Even if the universe began, why must a beginning have a cause? Time itself began; there was no “before” in which a cause could act. Causation is a concept inside the universe.

This is the strongest philosophical reply to the argument from a beginning. The theistic response is that a cause of the beginning of time need not be earlier in time, only prior in the order of dependence, the way (on some views) a cause can be simultaneous with its effect. Whether that is coherent is a live debate among philosophers of time. This claim deliberately stops short: it says the universe had a beginning and does not, by itself, say who or what caused it. The further step is argued in the Atheism case, where this objection is met head on.