Andrew Chignell recently proposed an original reconstruction of Kant's ‘Only Possible Argument’ for the existence of God. Chignell claims that what motivates the ‘Grounding Premise’ of Kant's proof, ‘real possibility must be grounded in actuality’, is the requirement that the predicates of a really possible thing must be ‘really harmonious’, i.e. compatible in an extra-logical or metaphysical sense. I take issue with Chignell's reconstruction. First, the pre-Critical Kant does not present ‘real harmony’ as a general condition of real possibility. Second, the real harmony requirement is not what motivates the ‘Grounding Premise’ of the proof. Instead, this premise is sufficiently motivated by what Chignell labels the ‘content’ requirement. Finally, Kant's downgrading of the proof in his Critical period is not based on a concern regarding the real harmony of the predicates of God, but on his Critical restrictions on cognition in general and modal cognition in particular.