While acknowledging the multiplicity of Ricoeur's works and of the subject-matter he has dealt with, the author emphasizes what he considers some of their constants: firstly, the rooting in the tradition of reflexive analysis (ch. 1); secondly, their «horizon» as suggested in the great genres of Plato's Sophist and understood in the light of the Aristotelian couple actus-potentia (ch. 2). He thus shows in which manner action (ch. 3) not only makes up a privileged theme of the philosophical reflection, but constitutes its very object, for it is in the action that the being-in-act exercises itself.