 It is to Burley’s credit that he is also able to distinguish between the intension and extension of complex expressions, as indicated by his distinction between a proposition habens esse subiectivum in intellectu and habens esse obiectivum in intellectu. In fact: (1) although the mental proposition exists in the mind as in a subject, the real proposition is present in the mind only qua object of the act of understanding; (2) the real proposition provides the objective content which the other kinds of proposition aim to express; and (3) the mental proposition is the semantic link between the spoken and written propositions on the one hand, and the real proposition they refer to on the other.