The development of "existentialism" in the last years of its leading French proponents, Jean-Paul Sartre and Maurice Merleau-Ponty, occurred in the areas of social philosophy and existential psychoanalysis in the case of Sartre and the philosophy of language and fundamental ontology for Merleau-Ponty. Partly in response to the latter's critiques, but chiefly as a result of his own political commitment, Sartre constructed a social ontology and a theory of history in his Critique of Dialectical Reason. Faithful to his existentialist emphasis on the primacy of the individual, but replacing his earlier philosophy of consciousness with one of praxis (roughly, purposive human activity in its historical and socioeconomic context), Sartre formulated a set of concepts, especially praxis, seriality, and the practico-inert, that respected the power of social forces to countermand, deviate, and reverse our undertakings without totally robbing the organic individual of existentialist freedom and responsibility. He allowed far greater play to the force of circumstance in assessing human action and underscored the determining power of family and early childhood experience in his massive existential biography of Gustave Flaubert, The Family Idiot. This last, combining the discourse of Being and Nothingness with that of the Critique, forms a kind of synthesis of Sartre's work.
At the time of his death in 1961 Merleau-Ponty was at work on a manuscript that has come to be known as The Visible and the Invisible, a work that some consider his version of Martin Heidegger's "What Is Metaphysics?" It reveals a growing interest in an ontology that avoids the pitfalls of "philosophies of consciousness," with their subject-object relation, which has defined and limited philosophy in the West for centuries. Inspired by the painter's articulation of the world and building on the concepts of chiasm and flesh, introduced in his earlier The Phenomenology of Perception, Merleau-Ponty was moving beyond the boundaries of phenomenology to elaborate an "indirect ontology" in which language questioning being questions itself.
