We totally misunderstand both his aims and his contribution if we try to read into Marx some anticipation of either the modest successes or the disastrous failures of those who later thought they were acting in his name.

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.

I think that both Mill and Sidgwick are great and admirable philosophers, from whom we still have a lot to learn. I would not favor a form of Kantianism (if there is such a form) that treats Mill's or Sidgwick's moral philosophy with disrespect.

Kant does not think that the silly commandment "universalize your maxims" is the be-all and end-all of ethics or that it provides us with some sort of general decision procedure that is supposed to tell us what to do under all circumstances.

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.

Both Kant and Fichte thought of traditions of revealed religion as ways of symbolically (that is, with aesthetic emotional power) thinking about our moral condition. Both thought that religion would become more and not less powerful, emotionally and morally, if the claims of scriptures and religious teachings were taken symbolically rather than literally (whatever 'literally' might mean in the case of claims that are either nonsensical or outdated or historically unsupportable if taken as metaphysical or historical assertions).

Marx's own illusion was to think that the working class movement, which he devoted his life to creating and strengthening, would both be socially and politically successful in the industrial nations of Western Europe, and that it would develop an entirely new way of human social life that would retain and even enhance the productive benefits of capitalism while overcoming the inhumanity and exploitation of capitalist social relations. Marx himself had no solutions to these problems. His object of study was capitalism itself.