Being an Nothingness: An Essay on Phenomenological Ontology (French: L'Être et le néant : Essai d'ontologie phénoménologique), sometimes subtitled A Phenomenological Essay on Ontology, is a 1943 philosophical treatise by Jean-Paul Sartre that is regarded as the beginning of the growth of existentialism in the 20th century. Its main purpose was to define consciousness as transcendent.