The basis of liberal democracy: Political not moral? Some critical remarks on Habermas's Principle D

The dilemma of liberal democracies in the domain of ethical and religious pluralism can be stated as follows: is it possible to define the principles grounding liberal democracy so that they can justify legitimacy and political obligation, without being dependent on particular moral contents?
Habermas’s proposal of Principle D is the most ambitious and promising solution to this dilemma of pluralism. It relies strongly on the non-moral character of principle D. But can this point be maintained without contradiction? The article tries to develop the thesis that it is impossible to conceive D as practical, normative and non-moral, as Habermas argues, because: (1) this interpretation generates contradictions within the theory itself; (2) D contains implicitly a reference to the moral point of view, otherwise it couldn’t assure an equal consideration of participants; (3) it is probably impossible, in general, to treat persons as equal without treating them as moral persons.