 RTT+COMP gives a compelling explanation. According to RTT+COMP, your ability to entertain the thought that p hinges upon your ability to bear appropriate psychological relations to a Mentalese sentence S whose meaning is that p. If you are able to think that John loves Mary, then your internal system of mental representations includes a mental sentence John loves Mary, composed of mental words John, loves, and Mary combined in the right way. If you have the capacity to stand in psychological relation A* to John loves Mary, then you also have the capacity to stand in relation A* to a distinct mental sentence Mary loves John. The constituent words John, loves, and Mary make the same semantic contribution to both mental sentences (John denotes John, loves denotes the loving relation, and Mary denotes Mary), but the words are arranged in different constituency structures so that the sentences have different meanings. Whereas John loves Mary means that John loves Mary, Mary loves John means that Mary loves John. By standing in relation A* to the sentence Mary loves John, you entertain the thought that Mary loves John. Thus, an ability to think that John loves Mary entails an ability to think that John loves Mary. By comparison, an ability to think that John loves Mary does not entail an ability to think that whales are mammals or an ability to think that \(56 + 138 = 194\).