The article explains Art. 19 II of the German Basic Law which guarantees that „in no case a basic right may be affected in its essence“. This guarantee has always puzzled judges as well as scholars because it leads into aporia, as many cases prove. This aporia is shown to be no fault of Art. 19 II GG, nor of the constitutional system as a whole. On the contrary, the aporetic norm is a remedy. It is a necessary opening clause (...) of the positive constitutional system to prevent existential breaches. Though rule of law as well as democracy inevitably require a systematic and logical order of positive law, this inevitable aim of the modern state will never be perfectly reached. Therefore, the state will always remain a menace that in rare but nevertheless realistic cases tends to destroy the liberties it should protect. Art. 19 II GG is the topical balance and equilibrium for this lack of a perfect system. Thus the aporetic norm turns out to be an important step in answer to the old question of philosophy, whether thinking and law-making have to be rational with Descartes, Kant, Merkl and Kelsen or topical with Aristotle, Cicero, Vico and Viehweg. (shrink)