Ludwig Wittgenstein (1889–1951) transformed philosophy of language twice over the course of his career. In the early Tractatus Logico-Philosophicus, he proposed the picture theory of meaning: propositions are logical pictures of facts, and language mirrors the structure of reality. From this view comes the famous proposition 5.6, "The limits of my language mean the limits of my world." Later, in the Philosophical Investigations, Wittgenstein abandoned this austere framework, arguing that meaning arises not from mirroring but from use. Words function as moves within language games, social activities in which their significance is determined by shared rules. The private language argument contends that a language understandable only to a single individual is impossible, because meaning requires public, intersubjective norms. Wittgenstein's later emphasis on the form of life — the broader cultural and social context in which language games are embedded — shows that understanding any utterance requires grasping the practices that give it sense.
Jean-Paul Sartre (1905–1980) gave existentialism its most famous formulation in the claim that existence precedes essence: humans have no predetermined nature, but exist first and then define themselves through their choices and actions. This leads to radical freedom: human beings are always free to choose, even in extreme circumstances, and are "condemned to be free." In Being and Nothingness, Sartre explores consciousness, freedom, and the nature of being through a phenomenological lens. The experience of the Look (le regard), being seen by another consciousness, transforms the self into an object and reveals the fundamental conflict at the heart of human relationships. Sartre names the resulting mood anguish: the awareness of one's radical freedom and total responsibility, with no external guarantee of meaning. To deny this freedom, to pretend one is determined by fixed identities or external forces, is to fall into bad faith (mauvaise foi), the self-deception of inauthentic existence.
Sartre's lifelong intellectual and romantic partner, Simone de Beauvoir (1908–1986), applied existentialist insights to the question of women's oppression. In The Second Sex, she argues that "one is not born, but rather becomes, a woman" — femininity is a social construction, not a biological destiny. Throughout history, de Beauvoir argues, man has been defined as the Subject and norm, while woman has been defined as the Other, a secondary and subordinate category. Applying existentialism to feminism, she insists that women must claim their freedom and transcendence rather than accept the passive, immanent roles imposed on them by patriarchal society. Her Ethics of Ambiguity deepens this line of thought, arguing that human freedom is inherently ambiguous: we are both free and situated, and genuine ethics requires embracing this ambiguity while willing freedom for all.