(2) _The New Science and His Own Discoveries._ Leibnitz was more fortunate than many of his contemporaries in that his university had already included in its curriculum the study of mathematics. At the age of fifteen he was devoting himself to mathematics at Jena, and he said that the study of Kepler, Galileo, and Descartes made him feel as though “transported into a different world.” Later in life he said of himself, that at fifteen he had decided to give up the scholastic theory of Forms for the mathematical explanation of the world. He became acquainted with the theories of Hobbes and Gassendi in 1670, when he was at Mainz. In 1672, at the age of twenty-six, when he was in Paris, he made himself possessor of all that the celebrated circle of Parisian scientists had to teach. He had gone to Paris a dualist; he returned to his native land with the Aristotelian teleology side by side in his mind with the Spinozistic conception of identity and necessity, the Spinozistic method, and the mathematical theory of the significance of infinitely small particles. The next ten years (1676–1686) were spent in overcoming his own dualism by systematizing these new theories acquired from so many sources. In 1680 he had universalized the concept of force so as to apply it to both souls and bodies. In 1684 he published his discovery of the differential calculus, in which he has had to share honors with Newton. In 1685 he asserted that the centres of force have individuality. He was led to this conclusion on account of the discovery of small organisms by the microscopes of Swammerdam and ♦Leeuwenhoek. In 1686 he successfully organized his collected material into his final system, although it was not until eleven years later (1697) that he called these centres “monads.” Probably he got the term “monad” not from Bruno, but from the mystic chemist, Van Helmont. Not only the content, but the form of his philosophy was determined by his mathematical studies. His philosophical diction is remarkably lucid. Mathematics reinforced his early resolve “in words to attain clearness and in matter usefulness.” His later discussions contain many terms that he had borrowed directly from mathematics. (3) _Political Pressure for Religious Reconciliation._ When Frederick the Wise of Saxony in 1519 refused the crown of Emperor, Germany was thrown into internal strife that in one hundred and thirty years destroyed all its material wealth and depopulated the country. This terminated in the Thirty Years’ War (1618–1648) and the Peace of Westphalia. Leibnitz was born two years before peace was declared. He was the first German scientist in two hundred years. Both Catholics and Protestants were weary of strife, and there was a general movement toward religious reconciliation. Thus religious amity was the most urgent public question.