Do we have a choice between political, metaphysical and moral justification in political philosophy?

Unlike natural sciences, where no other justifications than the facts of nature are required, political theories inevitably require justifications that could be reasonably expected to be accepted by the most ordinary men in their ways of thinking in their unavoidable interactions with each another. Elucidating the essential justifications of political theories is thus the core mission of political philosophy, which is also in fact what distinguishes between the philosophical doctrines of different political philosophers. In the history of political thoughts, various justificatory methods have been employed in political philosophy. While most classical political philosophers do not have a very strong tendency to classify their justifications as merely political, metaphysical or moral ones, modern political philosophers tend to classify theirs (or others’), as if we do have a choice between different kinds of justifications in matters of politics. Sadly, such classification never serves as much to clarify the differences between these justifications, as to serve as a way to devalue the philosophical claims of others. The first type of justifications being largely undervalued, if not detested, in modern political philosophy is undoubtedly those classified as metaphysical. A sentiment of resistance against political theories based on metaphysical claims stem from the historical events in the twentieth century, and was theorized by Isaiah Berlin who had been personally involved in these turbulences. According to his distinction of negative and positive liberty, those who fall under the positive camp are inescapably making claims of metaphysical truth, which in turn would be used by political opportunists for their own purposes. Though the intelligibility of such distinction has been questioned by other philosophers like Gerald MacCallum, the warning for caution associated with it never failed to influence other political philosophers ever since. John Rawls, who invoked the Kantian concept of noumenal selves in his earlier justificatory method of original position, came under attack from communitarians like Alasdair MacIntyre and Michael Sandel, who argue that his justification is based on metaphysical claims that are detached from social and historical contingencies. Rawls later adjusts his justificatory method, abandoning the apparent appeal to metaphysical claim, and adopts a new political justificatory method called overlapping consensus. Political philosophy, if the name should still be used, thus departs itself from metaphysical enquiries and draws itself closer to mere political claims which are questionably safer than their metaphysical counterparts. Moral justifications give way to political ones for similar reasons. Interpreted as sacrificing one’s own freedom and interests for the sake of others’, moral doctrines, such as Confucian philosophy, are seen as absolutely contradictory to our own liberty, and thus have been under attack from individualists, such as Robert Nozick, and their sympathizers. Kant’s philosophical philosophy, which obviously has metaphysical, moral and political elements at the same time, is thus critical in our pursuit of a plausible justificatory method in political philosophy. This paper aims to illustrate how Kant justifies his political doctrines and how these different elements find their appropriate places therein.