Leibnitz, German philosopher, mathematician, and man of affairs, born in Leipzig; studied law and took the degree of Doctor of Laws at Altorf; spent a good part of his life at courts, visited Paris and London and formed a friendship with the savans in both cities, and finally settled in Hanover, where he moved much in the circle of the Electress Sophia and her daughter Sophia Charlotte, the Prussian Queen, whom he entertained with his philosophy of the "infinitely little," as it has been called; he discovered with Newton the basis of the differential calculus, and concocted the system of monods (his "Monodology"), between which and the soul, he taught, there existed a "pre-established harmony," issuing in the cosmos; he was an optimist, and had for his motto the oft-quoted phrase, "Everything is for the best in the best of possible worlds"; his principal works in philosophy are his "Théodicée," written at the instance of Sophia Charlotte and in refutation of Bayle, and his "Monodologie," written on the suggestion of Prince Eugene (1646-1716).