A legal provision is “rigid” whenever amendment rules require more than a simple majority. While some constitutions are not rigid and can be modified by simple majority (as in the case of New Zealand), in other cases they include provisions that are super-rigid since they include unrevisable provisions (as in Germany, France, or Turkey). Political thinkers such as Kant, Condorcet, and Jefferson realized that constitutional rigidity might be objectionable. In particular, constitutional rigidity might be objectionable from an intergenerational point of view. The purpose of this paper is twofold. First, to offer a precise account of the intergenerational problem that constitutional rigidity raises. Second, to indicate the extent to which there can be intergenerational justifications for intergenerational rigidity, despite the problems it raises. The author insists in distinguishing intra- from inter-enerational rigidity, and “forward” from “backward” rigidity. These two distinctions play an important role in the argument.