The Dual‐Nature Thesis: Which Dualism?

According to Robert Alexy’s dual‐nature thesis, “law necessarily comprises both a real or factual dimension and an ideal or critical one.” I will suggest, first, that various dualisms need to be distinguished, in particular the empirical and the normative, the real and the ideal, the formal (procedural) and the substantive; second, that the dualism of the empirical and the normative and, within the latter, of the real and the ideal “ought,” is not specific to law but pertains to any normative system; and, third, that a dualism that distinguishes law from morality is a dualism of formal and substantive principles, which also serves to explain the authoritative character of law.