No theory about our bodies as mere objects of observation and calculation (as distinct from partners in communicative interaction, assumed to be free) can comprehend human nature.

The problem is that many who reject Marx do not read him, or read him only by bringing prejudices to their reading that prevent them from understanding him.

There is a very common, though also very silly, picture of Kant according to which as empirical beings we are not free at all, and we are free only as noumenal jellyfish floating about in an intelligible sea above the heavens, outside any context in which our supposedly "free" choices could have any conceivable human meaning or significance. Part of the problem here is that Kant faces up honestly to the fact that how freedom is possible is a deep philosophical problem to which there is no solution we can rationally comprehend.

For the utilitarian, there is a fact of the matter about the good (the general happiness, or whatever conception of the good the utilitarian adopts) and about which actions or moral rules would contribute to maximizing the good. For the rational intuitionist, there are truths about which actions should be done and not done.

If being "iron headed" is to be lacking such feelings, then Kant's position is that an ironheaded person could not be a moral agent because such a person would not be rational.

If the problem of free will is to see how freedom fits into the order of nature, then Kant's basic view about the free will problem is that it is insoluble.

It has taken me a long time to realize where I most disagree with Marx. His assessment of capitalism is far too favorable. He took its instability, inhumanity and irrationality to be signs that it was a merely transitional form, which had delivered into humanity's hands the means to a much better way of life than any that have ever existed on earth. Marx could not bring himself to believe that our species is so benighted, irrational and slavish that it would put up with such a monstrous way of life.