Camus studied philosophy at the University of Algiers, which brought him into contact with two of the major branches of 20th century philosophy: existentialism and phenomenology. Existentialism arises from an awareness that there is no pre-ordained meaning or order in the universe and that we must take responsibility for determining the meaning and order we are to give to our lives. Camus is particularly interested in religious existentialists, such as Kierkegaard (though such a label is not entirely fair to Kierkegaard), who conclude that there is no meaning to be found in human experience, and that this necessitates a "leap of faith" that places an irrational and blind faith in God.

Phenomenology, as advocated by Edmund Husserl, confines itself to observing and describing our own consciousness without drawing any conclusions regarding causes or connections. Like existentialism, phenomenology influenced Camus by its effort to construct a worldview that does not assume that there is some sort of rational structure to the universe that the human mind can apprehend.

This idea—that the universe has a rational structure that the mind can apprehend—characterizes an older trend in European philosophy called "rationalism." Rationalism traces its roots to René Descartes and to the birth of modern philosophy. Most of twentieth century European philosophy has been a direct reaction to this older tradition, a reactionary attempt to explore the possibility that the universe has no rational structure for the mind to apprehend.

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