Ideal ‘Ought’ and Optimization

The basis of principles theory is the norm-theoretic distinction between rules and principles. In A Theory of Constitutional Law (2002), I have defined rules as definitive commands and principles as optimization requirements. Against the definition of principles as optimization requirements the objection has been raised that optimization requirements are rules too because the optimization is definitively commanded. This chapter offers a reconstruction of the distinction between rules and principles that connects the concept of the ideal ‘ought’ with the concept of optimization requirement. In the language of mathematical logic, this is expressed by means of a ‘fundamental equivalence’. This equivalence is the basis of the author’s reply to all of the objections against his distinction between rules and principles.