I’ve just posted an item on Kant’s political writings at LiberalVision (LV is on the list of political blogs on the right). You’ll have to go there to see my summary of Kant and what I think he contributes to liberal thought, aimed at a thoughtful political audience rather than an audience of Kant scholars, or political theorists. I will just here add that Kant has of course been taken in many ways politically. As far as classical liberalism, or libertarianism is concerned, which is what LV promotes within the Liberal Democrats (UK political party), those who mention Kant in at least a partly favourable way include Friedrich Hayek and Ludwig von Mises, while Robert Nozick refers to Kant’s ethics in Anarchy, State and Utopia. Many left liberals (social liberals, new liberals, egalitarian liberals) have taken up Kant since T.H. Green in 19th century English liberalism, and a major influence on the ‘New Liberalism’ of the early twentieth century (constructive liberalism is think the equivalent phrase more used in Green’s own time). Recently John Rawls’ monument of egalitarian liberal philosophy, A Theory of Justice, claims a Kantian basis. Many Marxists have seen Marx;s philosophy as the inevitable outcome of German Idealist philosophy going back to Kant. This tends to involve taking further what some egalitarian liberals emphasise, which is the element of Kant which suggests that belonging to a moral community is prior in the human to individual interests, and moral judgements. Recently cosmopolitans and cosmopolitics tendencies have seen Kant as the precursor of global political institutions, global law and political action, and economic egalitarianism on a global level. The cosmopolitics people are more influenced by 20th century Continental European philosophy than the cosmopolitans.
I’ve got my views about the above, but I cannot go into detail there, I will just say that Kant’s specific comments on the scope and limits of government seem much closer to classical liberalism/libertarianism than left liberalism, Marxism or any other positions emphasising equality of wealth and income, and collective control of the economy. Kant clearly suggests that though the state should support the income of poorest, it should protect free trade and individual property, and should not try to change the patterns which emerge from individual actions.
For me, some of the most interesting commentary on Kant’s politics come from the discussion of Kant’s aesthetics as a model for political judgement. No time to go into that here, but Hannah Arendt and Samuel Fleischacker are the interesting names here, for me. Fleischacker belongs in between classical liberalism/libertarianism and egalitarian liberalism, leaning towards more towards the letter but with plenty of reservations and qualifications. Arendt is difficult to classify, but I certainly find it useful to think of her somewhere between the two major currents of liberal thought.