Is the universe a three-dimensional grid of space-time expanding from a size of zero along each dimension to some undetermined value that may be infinity if nothing interrupts the process of expansion? Spacetime=0 would be that singularity from which the Big Bang is said to have emerged, or does the universe emerge from a condition independent of space-time?
If existence cannot come from non-existence, but the space-time universe has a definite beginning, then existence must be independent of space-time. Existence may therefore be possible before time and beyond space, having none of the qualities contingent on either space or time. We may understand what such an existence is by simply knowing what it cannot be, by what space-time contingent qualities it may not possess.
Primordial existence (as we may call it) cannot have either size or shape; it cannot have location, neither inside (substance) nor outside (number, multiplicity). All such qualities are contingent on space-time. Primordial existence also cannot have any change in its essential nature, including that it can have no beginning nor end. If it is, as it must necessarily be, then it cannot cease to be. Furthermore, although it must incorporate the potential from which our universe arises, and perhaps from which countless other universes arise, it must nonetheless remain an undiminished initial condition from which such universes arise. All this is defined by the very nature of existence independent of space-time.
The standard cosmological model is consistent with this understanding of primordial existence, and it is quite reasonable to argue that something unchanging must ultimately be the source and initial condition of all space-time universes.