This concept of obligation is not restricted to actions. It is a concept of the “ought to be”. In order to explain the “ought to do”, Chisholm introduces another operator, ‘A’. ‘Ap’ expresses the idea that a person S succeeds in bringing about the state of affairs p. Making use this further expression, Chisholm defines the ought to do by saying that the statement that S ought to bring about some state of affairs p just means OAp.