An analysis of the epistemological structure of democratic deliberation as a procedure in which legal norms are constructed reveals that deliberation combines procedural and substantive aspects in a unique and inextricable manner. The co-original recognition of the private and public autonomy of all citizens provides the substantive critical standard against which the justice of norms is measured. At the same time, such recognition requires that the particular needs and values of all people concerned are taken into account. Given the privileged epistemic access people have to their own particular perspective, this requirement implies the ineliminability of actual deliberative procedures. The open-ended nature of these constructive procedures is partly due to the fact that the rules of the procedure are counterfactual and themselves subject to interpretation. More importantly, it also reflects the historical nature of our human world and the freedom of moral persons to shape and reshape their preferences.