ie.' Associated with Diderot in this vast enterprise, he was
at first, because of his eminent position in the scientific world, its
director and official head. He contributed a large number of scientific
and philosophic articles, and took entire charge of the revising of the
mathematical division. His most noteworthy contribution, however, is the
'Preliminary Discourse' prefixed as a general introduction and
explanation of the work. In this he traced with wonderful clearness and
logical precision the successive steps of the human mind in its search
after knowledge, and basing his conclusion on the historical evolution
of the race, he sketched in broad outlines the development of the
sciences and arts. In 1758 he withdrew from the active direction of the
'Encyclopedie,' that he might free himself from the annoyance of
governmental interference, to which the work was constantly subjected
because of the skeptical tendencies it evinced. But he continued to
contribute mathematical articles, with a few on other topics. One of
these, on 'Geneva,' involved him in his celebrated dispute with Rousseau
and other radicals in regard to Calvinism and the suppression of
theatrical performances in the stronghold of Swiss orthodoxy.

His fame was spreading over Europe. Frederick the Great of Prussia
repeatedly offered him the presidency of the Academy of Sciences of
Berlin. But he refused, as he also declined the magnificent offer of
Catherine of Russia to become tutor to her son, at a yearly salary of a
hundred thousand francs. Pope Benedict XIV. honored him by recommending
him to the membership of the Institute of Bologne; and the high esteem
in which he was held in England is shown by the legacy of L200 left him
by David Hume.

All these honors and distinctions did not affect the simplicity of his
life, for during thirty years he continued to reside in the poor and
incommodious quarters of his foster-mother, whom he partly supported out
of his small income. Ill health at last drove him to seek better
accommodations. He had formed a romantic attachment for Mademoiselle de
l'Espinasse, and lived with her in the same house for years unscandaled.
Her death in 1776 plunged him into profound grief. He died nine years
later, on the 9th of October, 1783.

His manner was plain and at times almost rude; he had great independence
of character, but also much simplicity and benevolence. With the other
French deists, D'Alembert has been attacked