What did Kant think the categorical imperative requires?

An excellent question. I discussed it at length in the fourth conversation, HG. In doing so, I explained the contradiction in Kant’s doctrine between his words about the categorical imperative, which are always perceived as the basis for humanistic (=human) morality, and his argument for the existence of God as the basis for morality. I explained that the categorical imperative has no validity without a source that gives it validity. His analysis assumes that there is a moral obligation and only discusses its limits, and thus arrives at the categorical imperative. But what is the basis for assuming that there is such an obligation, that does not appear there. It is a transcendental concept.