That something could come out of nothing would mean that there was a start point to existence, all existence:
You, me, ‘God’ (but then, He wouldn’t be God, if he had beginning of days), the planets etc would’ve all had an ultimate origin of nullity (somewhat like a null set in mathematics).
That’s like the way the big bang theory is generally regarded: a null set that yielded a nonempty set without undergoing any operation. (Forgive me here.) So if, say, whatever prompted the Big Bang was the start of it all, we can preach it as that that appeared out of nothing; that it had no cause.
Significantly, this admits the thought that everything could go back to nothingness, a cessation of existence. Imagine how the whole of the present and past reality might come to inexistence; compute it if you can.
Is it possible for all existence today to end up in a nihility of presence and manifestation. The total erasure of history?
If ‘nullity’ could happen tomorrow, it would say that nothing ever existed.
(And then, the big bang might happen again.)
Where does the paradox come up?
Where we believe nature that there’s always a cause, whether or not we know what it is and how it leads to its effects. The scientific method, therefore scientific research, runs on this assumption, looking to discover and explain patterns in nature and life.
If we agree that something leads to something, that leads to something … we say that there’s an infinitude of causality, hence, of existence. We thus also say that existence has always existed because there is existence now.
So it is becomes impossible for there ever to have been absolute nothingness. Why?
Because we exist.
This post has some coherence with “Agrippa’s Trilemma“, weighing the infinitude of causality argument etc.
That I am, or will be, means that I always have been.
That I shall never be, means that I always have never been.
The continuum of existence backwards into the past is a chain of causes; into the future, we have a chain of effects. So that the evolution of existence in all its dimensions is the progression and propagation of causes and effects—vitally mediated, severally, by the fundamental expression of volition, which is always a cause.