In literature, an apology/apologia is a work written in defense of an idea, system of thought, religion, etc., especially one that other people criticize. The Pensées were originally notes for a planned apology for Christianity.

“Concupiscence” comes from the Latin for “to desire strongly”; in theology, it refers to the human tendency to sin, resulting from the Fall. Blaise Pascal sees concupiscence as affecting mankind in many observable ways, resulting in contradictory and deceptive human behavior.

“Existentialism” refers to a school or branch of philosophy stressing the individual’s position as a self-determining agent responsible for his or her own choices. Although most often associated with non-religious philosophers of the 20th century who stressed the lack of an inherent meaning in life, aspects of this philosophical approach have also been attributed to earlier thinkers, including Pascal. The focus on the individual’s inner life and on humanity’s basic moral and spiritual condition in the Pensées are among its elements that could be considered related to existentialism.