  Precisely, the poet’s sin is to treat language as though it were a sound or a note; it is to treat language as a thing and to revere its materiality. This ignores the nature of linguistic expression, in which the signs must be traversed towards their signification. The reverse error is that of Paul Klee, who, according to Sartre, uses colour both as sign and as object (1948a, 23). The existentialist system of the arts is ordered according to the Hegelian principle where arts that involve language rule over the others, because they best express human freedom.