Without death we never can have idea about non existence. For us consciousness is same as life and existence. In physical existence we can notice consciousness only in bodies, therefore we conclude that destruction of the bodies means destruction of the consciousness.
Because everything exist trough consciousness or consciousness is all what it is, we conclude that with destruction of consciousness starts "something" what is "nothing".
What is nothing or non existence?
We even don't understand physical existence what we are in, how then we can talk or understand non existence what we are not in?
Idea about existence and non existence what we have now is in contradiction. Not only that we from emptiness, non activity, unconsciousness, total darkness (or who knows how else we imagine that non existence) can begin existence, but contradiction is also in existence of non existence.
Everything what exist is existence. If we say that non existence exist, then non existence also must be existence because exist. That means that exist only existence or constant change or interaction of opposites.
With death we can see that something opposite to physical existence exist. If we from idea of non existence what we have now (and what we formed only by physical existence and not directly) can't explain connection with physical existence (what must exist) means that our idea about non existence is not correct. One reason is also that we still don't understand physical existence, specially beginning.
Mistake is in that that we existence of consciousness connected only with existence of matter and on that way we represent physical existence as general idea about existence. Such general idea about existence can't have interaction of opposites without contradiction. General idea about existence must include in itself both opposites without contradiction.
But if idea of non existence is replace by non physical existence then contradiction disappear and law of interaction of opposites can explain beginning of physical existence.
On that way non existence or absolute emptiness is replace with non physical existence or absolute union, fullness, contraction or essence from what is possible beginning or expansion of differences, individuality or appearance of forms or physical existence.
Non existence or unconsciousness, non meaning and absolute individuality as base of anything is impossible. Non meaning and unconsciousness can exist only in frame of consciousness, union and meaning as necessary opposite for interaction.
For physical existence is characteristic law of cause and effect. Everything inside physical existence can be explain by that law except beginning. For beginning that law is contradict or everything points on limitation (not on generality ) of that law and necessity of existence of opposite or non physical law. On that way consciousness or non physical existence can be only possible and essential explanation of beginning of physical existence.