In this collection of texts from the late 1970s, now updated for the first time and supplemented with a foreword by the author in German, Jean-Luc Nancy explores the origin of the modern subject. The famous Cartesian formula "I think" gives birth to the "representational subject," which possesses truth and certainty. However, by substantializing the pure act of expression "I think," Descartes strips this subject of any content and existentiality in the modern sense. The ego as a punctual identity is a subject that can neither doubt nor meditate. Cartesian thinking is shaken by the contradiction that arises between the incompleteness of the thinking substance and the living subject that writes, lives, and experiences. This shaking is already present as a fundamental paradox in Descartes' own thinking.