Discursive theories of justice have been questioned for putting forward high-level principles that should nevertheless play a role in practical discourses in which the justice of a claim is at stake. Here, I will critically examine and systematize the main tenets in Rawls’s and Habermas’s discursive theories, and will suggest that the principles of justice (Rawls) and universalization (Habermas) can and play the role of mandates of optimalization in real deliberations on justice.