Collected here are the written traces of courses on the concepts of nature given by Maurice Merieau-Ponty at the College de France in the 1950s--notes that provide a window on the thinking of one of the most influential philosophers of the twentieth century. In two courses distilled by a student and in a third composed of Merieau-Ponty's own notes, the ideas that animated the philosopher's lectures and that informed his later publications emerge in an early, fluid form in the process of being eleborated, negotiated, critiqued, and reconsidered.