The purity of a being is never unconditional or absolute

It is a mistake to postulate anywhere a purity that exists in itself and needs only to be preserved.... The purity of a being is never unconditional or absolute; it is always subject to a condition. This condition varies according to the being whose purity is at issue; but this condition never inheres in the being itself. In other words: the purity of every (finite) being is not dependent on itself... For nature, human language is the condition of its purity that stands outside of it.

Walter Benjamin, The Correspondence of Walter Benjamin (University of Chicago Press, 1994) p. 206