his later career, Sartre attempted to reconcile the existential philosophy of Søren Kierkegaard with Marxist philosophy and Hegelian dialectics in his work Critique of Dialectical Reason. Sartre was also involved in Marxist politics and was impressed upon visiting Marxist revolutionary Che Guevara, calling him "not only an intellectual but also the most complete human being of our age". Louis Althusser Louis Althusser (16 October 1918 – 22 October 1990) was a Marxist philosopher. He was a longtime member and sometimes strong critic of the French Communist Party. His arguments and theses were set against the threats that he saw attacking the theoretical foundations of Marxism. These included both the influence of empiricism on Marxist theory and humanism and reformist socialist orientations which manifested as divisions in the European Communist parties as well as the problem of the cult of personality and of ideology itself. Althusser is commonly referred to as a structural Marxist, although his relationship to other schools of French structuralism is not a simple affiliation and he is critical of many aspects of structuralism. His essay Marxism and Humanism is a strong statement of anti-humanism in Marxist theory, condemning ideas like "human potential" and "species-being", which are often put forth by Marxists, as outgrowths of a bourgeois ideology of "humanity". His essay Contradiction and Overdetermination borrows the concept of overdetermination from psychoanalysis to replace the idea of "contradiction" with a more complex model of multiple causality in political situations (an idea closely related to Gramsci's concept of hegemony). Althusser is also widely known as a theorist of ideology and his best-known essay is Ideology and Ideological State Apparatuses: Notes Toward an Investigation. The essay establishes the concept of ideology, also based on Gramsci's theory of hegemony. Whereas hegemony is ultimately determined entirely by political forces, ideology draws on Sigmund Freud's and Jacques Lacan's concepts of the unconscious and mirror-phase respectively and describes the structures and systems that allow us to meaningfully have a concept of the self. Structural Marxism Structural Marxism is an approach to Marxism based on structuralism, primarily associated with the work of the French theorist Louis Althusser and his students. It was influential in France during the late 1960s and 1970s and also came to influence philosophers, political theorists and sociologists outside France during the 1970s. Neo-Marxism Neo-Marxism is a school of Marxism that began in the 20th century and hearkened back to the early