In the late 1970s and 1980s, Louis Althusser endured a period of intense mental instability during which he murdered his wife and was committed to a psychiatric hospital. Spanning this deeply troubling period, this fourth and final volume of political and philosophical writings reveals Althusser wrestling in a creative and unorthodox fashion with a whole series of theoretical problems to produce some of his very finest work. In his profound exploration of questions of determinism and contingency, Althusser developed a philosophy of the encounter, which he links to a hidden and subterranean tradition in the history of Western thought which stretches from Epicurus through Spinoza and Machiavelli to Marx, Derrida and Heidegger.