Being is prior to nothingness and establishes the ground for it … it is from being that nothingness derives concrete efficacy. This is what we mean when we say that nothingness haunts being.
Men are what they are not, and are not what they are.
Man is the being through whom nothingness comes to the world.
Nothingness exists between consciousness and its object.
Non-being exists only on the surface of being.
Nothingness lies coiled in the heart of being – like a worm.
'Being and Nothingness', J P Sartre (1943)