# Blaise Pascal

### French theologian, mathematician, and philosopher

# Biography

Pascal was born in Clermont-Ferrand on June 19, 1623, and his family settled in Paris in 1629. Under the tutelage of his father, Pascal soon proved himself a mathematical prodigy, mastering Euclid's Elements by the age of 12. At the age of 16 he formulated one of the basic theorems of projective geometry, known as Pascal's theorem and described in his *Essai pour les coniques* (Essay on Conics, 1639).

In 1642 he invented the first mechanical adding machine. Pascal proved by experimentation in 1648 that the level of the mercury column in a barometer is determined by an increase or decrease in the surrounding atmospheric pressure rather than by a vacuum, as previously believed. This discovery verified the hypothesis of the Italian physicist Evangelista Torricelli concerning the effect of atmospheric pressure on the equilibrium of liquids. Six years later, in conjunction with the French mathematician Pierre de Fermat, Pascal formulated the mathematical theory of probability, which has become important in such fields as actuarial, mathematical, and social statistics and as a fundamental element in the calculations of modern theoretical physics. Pascal's other important scientific contributions include the derivation of Pascal's law or principle, which states that fluids transmit pressures equally in all directions, and his investigations in the geometry of infinitesimals.

In 1647, a few years after publishing *Essai pour les coniques* he suddenly abandoned the study of mathematics. Because of his chronically poor health, he had been advised to seek diversions from study and attempted for a time to live in Paris in a deliberately frivolous manner. His interest in probability theory has been attributed to his interest in calculating the odds involved in the various gambling games he played during this period.

At the end of 1654, after several months of intense depression, Pascal had a religious experience that altered his life. He entered the Jansenist monastery at Port-Royal, although he did not take orders, and led a rigorously ascetic life until his death eight years later. He never published in his own name again. The Jansenists encouraged him in his mathematical studies, which he resumed. To assist them in their struggles against the Jesuits, he wrote, under a pseudonym, a defense of the famous Jansenist Antoine Arnauld, the famous *Lettres provinciales* (Provincial Letters), in which he attacked the Jesuits for their attempts to reconcile 16th-century naturalism with orthodox Roman Catholicism. His most positive religious statement appeared posthumously (he died August 19, 1662); it was published in fragmentary form in 1670 as *Apologie de la religion Chrétienne *(Apology of the Christian Religion). In these fragments, which later were incorporated into his major work, he posed the alternatives of potential salvation and eternal damnation, with the implication that only by conversion to Jansenism could salvation be achieved. Pascal asserted that whether or not salvation was achieved, humanity's ultimate destiny is an afterlife belonging to a supernatural realm that can only be known intuitively.

Pascal's most famous work is the *Pensées *(published 1670), a set of deeply personal meditations in somewhat fragmented form on human suffering and faith in God. In the *Pensées* he attempted to explain and justify the difficulties of human life by the doctrine of original sin, and he contended that revelation can be comprehended only by faith, which in turn is justified by revelation. "Pascal's wager" expresses the conviction that belief in God is reasonable on the ground that there are no rational grounds either for belief or disbelief, so belief is not less reasonable than disbelief; but this being so it is wiser to gamble on the truth of religion since this policy involves success if religion is true and no significant loss if it is false. He had admirers both Roman Catholic and Protestant, including John Wesley, the founder of Methodism, who praised an essay he wrote on the psychology of conversion. Pascal died at the age of 39 from a combination of tuberculosis and stomach cancer.