Fermat applied his method of tangents to many difficult problems. The method has the form of the nowstandard method of differential calculus, though it begs entirely the difficult theory of limits .

Pascal is called the founder of modern probability theory. He earns this title not only for the familiar correspondence with Fermat on games of chance, but also for his conception of decision theory, and because he was an instrument in the demolition of probabilism, a doctrine which would have precluded rational probability theory.
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