 In Fourth Replies Descartes say that his reason for mentioning God’s power in the Sixth Meditation proof of real distinction is to remind his reader that our clear and distinct perceptions are veridical (AT 7:226, CSM 2:159). In the Sixth Meditation itself he arrives at a clear and distinct perception of mind as an immaterial substance and body as a material non-thinking substance and is immediately struck by the union of his mind and body: “It is true that I may have… a body that is very closely joined to me” (AT 7:78, CSM 2:54). He says that “nevertheless” his mind and body are really distinct. Descartes appreciates that the facts of mind-body union and mind-body separation are  opposed.[41]  In the context of demonstrating the real distinction between mind and body he reminds us that God’s power is such that there can be creatures that have nothing in common but that are intimately  united.[42]