[I cannot say it better than the author I learned it from, so I won't try.]
Existence is a self-sufficient primary. [This is why it "must" exist.] It is not a product of a supernatural dimension [a creator], or of anything else. There is nothing antecedent to existence [nothingness], nothing apart from it—and no alternative to it. Existence exists—and only existence exists. Its existence and its nature are irreducible and unalterable. Leonard Peikoff "The Analytic-Synthetic Dichotomy,"
Introduction to Objectivist Epistemology, 148
A vulgar variant of concept stealing, prevalent among avowed mystics and irrationalists, is a fallacy I call the Reification of the Zero. It consists of regarding "nothing" as a thing, as a special, different kind of existent. (For example, see Existentialism.) This fallacy breeds such symptoms as the notion that presence and absence, or being and non-being, are metaphysical forces of equal power, and that being is the absence of non-being. E.g., "Nothingness is prior to being." (Sartre)—"Human finitude is the presence of the not in the being of man." (William Barrett)—"Nothing is more real than nothing." (Samuel Beckett)—"Das Nichts nichtet" or "Nothing noughts." (Heidegger). "Consciousness, then, is not a stuff, but a negation. The subject is not a thing, but a non-thing. The subject carves its own world out of Being by means of negative determinations. Sartre describes consciousness as a 'noughting nought' (néant néantisant). It is a form of being other than its own: a mode 'which has yet to be what it is, that is to say, which is what it is, that is to say, which is what it is not and which is not what it is.'" (Hector Hawton, The Feast of Unreason, London: Watts & Co., 1952, p. 162.)
(The motive? "Genuine utterances about the nothing must always remain unusual. It cannot be made common. It dissolves when it is placed in the cheap acid of mere logical acumen." Heidegger.) Introduction to Objectivist Epistemology, 80