The most important task is to distinguish clearly between the three notions of nothing, negation, and non-being. This task is urgent because of the confusion that surrounds these notions in existentialism. Non-being is negated being. It consists of two fundamental ingredients: being and negation. The difference between being and non-being is comparable to the contrast between the property of being square and the ‘property’ of being non-square. Negation of existence always amounts to the denial that the something in question is identical with an existent. Negation disappears from states of affairs and reappears in the mind in the form of a ‘negating’ mental act of denial. To every positive state of affairs, there is coordinated precisely one negative state of affairs which is its negation. Negation is a relation between states of affairs. It exists in the world as truly as any other relation.