Some of Kant's particular moral opinions, either because he shared the prejudices of his time, or because of his own personal crotchets, can strike sensible people as ridiculous or offensive. But in my view, his own theory provides us with the resources (the best resources available, I believe) to correct his own personal errors or cultural prejudices.
Allen W. WoodThere is no author or legislator of the moral law. It is simply valid in itself in the nature or essence of things. We become autonomous only when we obey it, because then our will aligns itself with the objectively valid law, and our choice follows the same law as that we give ourselves. We can think of rational faculty (or the idea - the pure rational concept, not exhibitable in experience) as the legislator or author of the law because reason recognizes an objective standard, and to that extent is already aligned with objective moral truth.
Allen W. WoodIt is actually a nice question how far Descartes himself endorses the monological and metaphysically dualistic theory of mind associated with his name and his legacy in early modern philosophy. But Fichte does reject this tradition, by suggesting that an immaterial thinking substance is an incoherent notion, and a rational being whose rationality was not developed through communication with others is a transcendental impossibility.
Allen W. WoodWe usually can't know how, and we probably should not even ask, how our lives contribute to a better world.
Allen W. WoodKant's description of most ethical duties reads more like a description of moral virtues and vices. Once we see this, we see that Kantian ethics is indeed a kind of virtue ethics, and that it does not "divide the heart from the head" (to anticipate one of your later questions) but instead recognizes the deep truth that reason and emotion are not opposites.
Allen W. Wood