Kant opens the discussion of this "disagreement" by reference to the point that morals is practical of itself, a contention that clearly refers back to the whole account of practical reason in The Critique of Practical Reason. In making this point Kant refers in passing to the general claim that "ought" implies "can". The point of these initial references is to make the claim (in contrast to some contemporary readings of Kant's practical philosophy) that morals and politics belong together as distinct parts, as he here puts it, of "doctrine of right" (Ak. 8: 370). Morals is now presented as the theoretical part of this doctrine with politics described as the doctrine of right put into practice. This does involve a distinction in some sense between what Kant will put out in the Doctrine of Right as a theory and politics as conventionally understood. So there is some form of relation that needs to be mapped (as is also apparent from Kant's essay on theory and practice).
The relationship that Kant maps between morals and politics thus understood is subsequently condensed into two statements. Politics is presented as based on the statement that we should be wise as serpents whilst morals is indicated to limit the application of this statement (thus in a sense to schematise it) by means of the condition that we be also as guileless as doves. Both need to be able to exist together if there is not to be a conflict between politics and morals.
The problem of the origin of the conflict is next traced to the attitude of the "practical man" who takes morals to be only theory. This person adopts the view that it is pointless to will the conditions of perpetual peace due to a claim concerning human nature. After a careful rendition of contractarian reasoning Kant points to the point that is at issue here which concerns the nature of power. The claim of the practical man is to the effect that the one who holds power will not let the prescription of laws be based on the ground of the social contract. Further, that states, once independent, will not be constrained by reference to other states. These claims rest on an appeal to political prudence and empirical principles of human nature. It is the combination of the "prudent" attitude and the purely empirical view of humanity that is the ground of this "realist" position, the same position still adopted in various guises in contemporary IR theory. Subsequent postings will trace further Kant's account of the problems he takes this view to have.