Blaise Pascal
1623 CE – 1662 CE · Early Modern Era
“The heart has its reasons which reason knows nothing of.”
Biography
Blaise Pascal was a mathematical prodigy who at sixteen wrote a treatise on conic sections that startled the Parisian mathematical community and who invented one of the first mechanical calculators (the Pascaline) to help his father, a tax commissioner, with arithmetic. He made basic contributions to probability theory, hydraulics, and the physics of the vacuum, corresponding with Fermat and astonishing the Parisian scientific community. In 1654, he had an intense mystical experience, the 'Night of Fire', which he recorded on a scrap of parchment sewn into his coat for the rest of his life. He largely abandoned mathematics and science, joined the Jansenist community at Port-Royal, and devoted his remaining years to philosophy and Christian apologetics. His Pensées, fragmentary notes for a planned defense of Christianity, published posthumously, are dense with sharp observations on human nature, faith, and the limits of reason. He died at thirty-nine, his great work unfinished.
Major Works
Key Arguments
Click “Philosophy 101” to read the full exploration of each argument.
Pascal's Wager
Pascal posed the question of belief in God not as a matter of proof but as a matter of practical decision under uncertainty. You must choose, belief or unbelief, and you cannot avoid choosing, because not choosing is itself a choice. If God exists and you believe, you gain infinite happiness (eternal life). If God exists and you do not believe, you suffer infinite loss (eternal damnation). If God does not exist, the believer loses very little (some finite pleasures), while the unbeliever gains very little. When you calculate the expected value of the two options, belief dominates: it offers infinite potential reward against finite potential cost. Pascal was not arguing that this proves God exists, he was arguing that, given unavoidable uncertainty, wagering on God is the rational choice. Critics have objected that you cannot simply will yourself to believe, that the argument applies equally to any religion's God, and that genuine faith cannot be reduced to a bet.
Why it matters: Founded decision theory and the application of probabilistic reasoning to practical life. The Wager is still debated in philosophy of religion and introduced concepts fundamental to game theory, expected utility, and risk analysis.
The Two Infinities
In a central passage of the Pensées, Pascal asked the reader to contemplate humanity's position in the universe. Look outward: the visible world is an infinite expanse, and even that is merely a speck within the incomprehensible vastness of the cosmos. Now look inward: within the smallest visible object lies an abyss of still smaller structures, an infinity in the other direction. Human beings are suspended between these two infinities, the infinitely large and the infinitely small, comprehending neither, grasping at a middle ground that is itself vanishingly tiny in relation to both extremes. We are, Pascal wrote, 'a Nothing in comparison with the Infinite, an All in comparison with the Nothing, a mean between nothing and everything.' This is a philosophical meditation on the human condition: we are creatures who desperately want to understand the universe but whose position within it makes comprehensive understanding impossible.
Why it matters: A meditation on human finitude and the limits of knowledge that anticipated existentialist themes of anxiety and cosmic insignificance. It also expressed a genuinely scientific humility, Pascal was one of the first thinkers to grasp the implications of the new physics for humanity's self-understanding.
The Heart and Reason
Pascal argued that the dominant philosophical tradition, from Descartes in his own time back through Aristotle, was wrong to treat reason as the sole or supreme path to truth. 'The heart has its reasons which reason knows nothing of,' he wrote. By 'the heart' he did not mean mere emotion or sentiment but a mode of immediate, intuitive knowledge that grasps first principles directly, truths like the reality of space, time, and number that we know with certainty but cannot prove through logical deduction (any attempt to prove them must assume them). Reason operates within the framework these intuitions provide but cannot establish the framework itself. Pascal extended this to religious knowledge: the existence of God, he argued, is not the kind of truth that yields to logical demonstration, yet it can be known through the heart, through direct experience, moral intuition, and what Pascal called the 'infinite abyss' in human consciousness, an emptiness that nothing finite can fill.
Why it matters: Challenged the Cartesian confidence in pure reason and opened a philosophical space for non-rational ways of knowing that deeply influenced Kierkegaard, William James, and the existentialist tradition. The tension Pascal identified between reason and the heart remains central to epistemology and philosophy of religion.
Lasting Influence
Founded probability theory and decision theory. His Pensées influenced Kierkegaard, existentialism, and philosophy of religion.
Your Reading Path
The Companion Guide
Seven eras of philosophy in one volume — reading lists, key terms, journal prompts · $19.99