This paper is my contribution to round three of a longstanding debate between Robert Alexy and me about the principles theory’s concept of principle. In the first round, Alexy—bucking tradition—proposed a nongradualist distinction between rules and principles that divided the ontology of norms into two categorically distinct norm‐types. He connected this norm‐theoretical analysis with a theory of fundamental rights according to which such rights had to be understood as principles and thus interpreted as optimization requirements. In the first round I (...) objected to the norm‐theoretical assumptions and questioned the doctrinal merit of the principles theory approach. Unlike Alexy, I saw no merit in his notion of principle over and above optimization requirements, which by that time Alexy, too, regarded as rules. In round two, Alexy defended his concept of principle by taking refuge in the notion of an ideal ought, which he defined as a command to be optimized. In this second round, I criticized the new attempt to save his view of principles on the ground that the norms Alexy had in mind optimized not commands but states of affairs and thus were ordinary norms or rules according to the misguided taxonomy of the principles theory. Alexy opened round three of our exchange by admitting that my critique of round two was justified and that he had erred in identifying principles as ideal commands to be optimized. He now proposes an index theory of principles. In the paper, I recapitulate the motive and the main points of our debate and scrutinize Alexy’s latest innovation. (shrink)