The Big Bang is a mathematical model, derived from Einstein’s field equations and subsequently supported by observation.
Theoretical physicist, mathematician and Nobel Laureate Roger Penrose, has modelled a cosmological concept wherein ours is one of a chain of recurring universes. Penrose says the maths checks out (if anyone is qualified to make such a claim, it’s him). But the model is not supported by observation, and may in principle be unfalsifable. So yes, at this point we are deep into philosophy and some distance from empirical science. As we are bound to be when, both literally and metaphorically, we find ourselves looking out over vast oceans of space and time.