Being (n.) is an impossible goal which forms a self-estrangement that is part of the human condition (whereas for heidegger being is a constantly receding origin from which we are estranged).
Being (n.) is and non-being is not because being is logically prior to non-being and non-being exist only as a negation of being, as a borrowed being.
Being (n.) is fundamental and does not depend on anything else for its being, whereas non-being, the negation of being, is entirely dependent on being for its borrowed existence.
Being (n.) is that which man, as he is born into a material universe that precedes him, is inserted into.