The Theatre of Cruelty has been created in order to restore to the theatre a passionate and convulsive conception of life, and it is in this sense of violent rigour and extreme condensation of scenic elements that the cruelty on which it is based must be understood. This cruelty, which will be bloody when necessary but not systematically so, can thus be identified with a kind of severe moral purity which is not afraid to pay life the price it must be paid.

The Theatre of Cruelty, in The Theory of the Modern Stage (ed. Eric Bentley) (1968).