  This changed, however, in 1672, when Leibniz was given the single most important opportunity of his life: the Elector of Mainz sent him on a diplomatic mission to Paris, the center of learning and science at the time. Leibniz was able to stay in Paris for four years (with a brief trip to London in 1673), during which time he met many of the  major figures of the intellectual world, among them   Antoine Arnauld,  Nicholas Malebranche,   and,  most important, the Dutch mathematician and physicist,   Christiaan Huygens.   It was he, “the great Huygenius” (as John Locke would call him in the Dedicatory Epistle to his Essay Concerning Human Understanding), who took Leibniz under his wing and tutored him in the developments in philosophy, physics, and mathematics. Not only was Leibniz able to converse with some of the greatest minds of the seventeenth century while in Paris, he was also given access to the unpublished manuscripts of Descartes and Pascal. And, according to Leibniz, it was while reading the mathematical manuscripts of Pascal that he began to conceive what would eventually become his differential calculus and his work on infinite series. In this time, Leibniz also designed a calculating machine able to perform addition, subtraction, multiplication, and division (see the Other Internet Resources for a picture).  And his trip to London in 1673 was meant in part to present his designs to the Royal Society.