What is essential to acting morally is not fulfilling some rule about outward appearances, but rather being motivated in the right way, that is, by the motive of duty. There is no way that we can explain this motive further, for it is equivalent to causation from the noumenal world, and none of our concepts are applicable to that world. We can, though, talk about the effect of the moral motive on the rest of our psychology.
We humans are naturally inclined to follow self-love, that is, to strive to please ourselves by satisfying our desires. We are also inclined to self- conceit, to thinking that just by virtue of being oneself one is at the center of the universe and deserves to do whatever one pleases. The moral law strikes down these feelings, making us aware that we cannot do whatever we please. We also feel pain when the moral law forces us to leave our desires unsatisfied. On the other hand, the strength of the moral law to overcome our desires awakens respect for it. This combination of personal humiliation and respect for the law is the peculiarly moral feeling. However, this moral feeling is not the incentive to act morally but rather only the accompaniment of acting morally, for only the idea of duty can be the right motivation.
Respect, in particular, is a distinctively moral feeling. All sorts of things, ranging from talented people to majestic mountains can produce the similar feelings of awe and admiration. But only the operation of the moral law can produce respect. We see this when we think first of the talented but morally bad person and then of the humble but morally upright person. We feel admiration for the first person but no respect, while we cannot help but respect the latter, even if we might rather affect an air of superiority.
The correct incentive is obedience to the moral law, and not love of the moral law. For to act morally because we like to is to make one's adherence to the moral depend on one's continued liking of it and continued pleasure at satisfying it, which is not consistent with true morality. God's will is a "holy will," which naturally follows the moral law. Since God has no urges to disobey the moral law, it is not even really a law for him. This is not true for humans, though, and it is arrogant to act as though it was. We must therefore be prepared to obey the law no matter how we feel about it.
This sort of action is free, undetermined by empirical incentives and caused noumenally. What then of the theories that we can understand freedom in terms of this world? They have a general flaw, in that this world is a series of events with later events caused by the earlier. My physical state, which supposedly freely causes an action, is the result of the distant past over which I have no control. So if the physical world was all there is, the action would be caused by the past that I cannot control, and it would be outside my control. My freedom would at best be like the freedom of a clock that can follow its mechanisms without interference once it has been wound. However, since the human being exists also in the noumenal world, there can be real freedom. Even if my present actions are caused by the past, if I exist outside time, I could have created the whole sequence of events differently. This is why it makes sense to repent for past bad deeds, and why we place moral blame even on those whose character is unchangeably bad.
Investigation into the moral leads us to see the value of recognizing a distinction between the phenomenal and the noumenal, with space and time adhering to the phenomenal and freedom requiring the noumenal. These are the same results as those of the independent investigations of the first Critique, and so the first and the second Critiques lend each other support.