The doctrine of propositions, internalism, and global supervenience

I present two short arguments concerning the views named in the title. First, I argue that the Doctrine of Propositions, according to which the contents of our psychological attitudes are always propositions, is incompatible with Internalism, understood as a doctrine endorsing the intrinsic character of mental content. Second, I try to show that the Doctrine of Propositions is also incompatible with the claim that psychological properties supervene globally on physical properties (i.e., that there can be no mental difference without some physical difference). The upshot is that the Doctrine of Propositions is inconsistent with each of two important supervenience principles.