Fichte takes an I or free will to be not a thing or being but an act which is not undetermined but self-determined, in accordance with reasons or norms rationally self-given.

In fact, if you read what Kant has to say about feeling, desire and emotion, you see that he is not at all hostile to these. He is suspicious of them insofar as they represent the corruption of social life (here he follows Rousseau), but he also thinks a variety of feelings (including respect and love of humanity) arise directly from reason - there is, in other words, no daylight between the heart and the head regarding such feelings.

We can't coherently deny, or even decline to affirm, that we are free.

What Smith and Marx have in common is that they were both philosophers of great vision and perceptiveness, deep humanity, and a sense of social reality that has been lost in the abstractly formalistic economic theories that have dominated the field since the last third of the nineteenth century.

Kant regards the universalizability test for maxims as focused on a very special sort of situation: one where the agent is tempted to make an exception to a recognized duty out of self-preference. The universalizability test is supposed help the agent to see, in a particular case of moral judgment, that self-preference is not a satisfactory reason for exempting yourself from a duty you recognize. Kant thinks, as a matter of human nature, that this situation arises often enough and that we need a canon of judgment to guard against it.

In fact people do not know enough about themselves and what is good for them to form a sufficiently definite conception of the general happiness (or whatever the end is) to establish definite rules for its pursuit.

Kant does represents a distinctively modern view of the human condition in contrast to that of ancient high culture, found in ancient Greek ethics and also in ancient Chinese ethics.