Computer historians recognise his contribution to the field by his construction of a mechanical calculator capable of addition and subtraction at the age of 18. He also produced a treatise about conic sections as a young man. In 1654, prompted by a friend interested in gambling problems, he corresponded with Fermat and laid out a simple account of probabilities.
His notable contributions to the fields of the study of fluids (hydrodynamics and hydrostatics) were centered around the principles of hydraulic fluids. His inventions include the hydraulic press (using hydraulic pressure to multiply force) and the syringe. He clarified concepts such as pressure (the unit of which bears his name) and vacuum.
Following a profound religious experience in 1654 Pascal abandoned mathematics and physics for philosophy and theology. His most influential work, the Penseeswas never completed, but a version of his notes for that book were published under the name in 1670 8 years after his death, and it soon became a classic of devotional literature, was published posthumously.
Pascal is also known for his attack on Casuistry as a popular ethical method used by Catholic thinkers in the early modern period, (especially the Jesuits) as the mere use of complex reasoning to justify moral laxity.
See also: Pascal's wager