Blaise Pascal was a French philosopher, mathematician, scientist, inventor, and theologian who made significant contributions in various fields. He was a pioneer in game theory and probability theory in mathematics, and in existentialism in philosophy. Pascal was also a defender of Christianity and wrote extensively on theology and religion. Despite suffering from chronic illness, Pascal contributed to mathematics and physical science through experimental and theoretical work on hydraulics, atmospheric pressure, and the existence and nature of the vacuum. He championed strict empirical observation and controlled experiments in science and opposed rationalism and metaphysical speculations. After experiencing a mystical illumination and midnight conversion in 1654, Pascal turned his attention almost exclusively to religious writing. He wrote the Lettres Provinciales, a satirical attack on Jesuit casuistry and a defense of Jansenism, and the Pensées. These two literary works, along with his scientific writings, have attracted the admiration and critical interest of philosophers and readers in every generation.

The Pensees is a collection of writings that were intended as a defense of Christianity, but Pascal died before it could be fully edited and published. As a result, the Pensees is a series of fragments rather than a grand treatise. Pascal emphasizes the natural depravity of human beings in the Pensees. He argues that humans are inordinately concerned with themselves and that the self, if left unchecked, will destroy the individual. Only God's grace can bring about salvation, and no one can be redeemed from the self without aid from God. Despite man's wretchedness, because he is made in God's image, he possesses greatness and something to really be proud of. Pascal sees man's sinfulness as a reason to hate mankind but man's likeness to God as a reason to love mankind. He argues consistently throughout the Pensees that only when one accepts the dual nature of humanity, the dark and the light, can one truly make sense of the world.

Pascal also discusses some social, political, and moral matters in the Pensees. He criticizes the behavior of the leadership of the Catholic Church but maintains the truth of their theology. He claims that all of morality is conventional and based in human power to maintain the social order. Pascal claims that custom motivates most of our actions. He expresses disdain for a general culture of being uninterested in ultimate matters and in ignoring the gravity of one's eternal fate. Pascal is consistently concerned with the relationship between faith and reason. He thinks that the two must be used together, but reason alone can bring no one to faith. Only God can do that. However, there is a partial exception in the most famous part of the Pensees, Pascal's Wager. Pascal's Wager is a probabilistic argument for God's existence. Supposing that belief in God gets one to heaven and disbelief sends one to hell, it is rational to "wager" by believing in God. Pascal thinks that making the wager is unavoidable and that while belief cannot come to a man by will alone, if he is convinced by the wager, he can begin to engage in Christian practice until his belief begins to bend around his practices.