Comte, the French Positive philosopher, accomplished the bulk of his work after recovering from an attack of insanity during which he threw himself into the Seine. Perhaps it is too soon to judge of the ultimate value of his system of philosophy. It has had impassioned adherents as well as scornful critics. His main thesis seems to be “that the improvement of social conditions can only be effected by moral development and never by any political mechanism, or any violence in the way of an artificial redistribution of wealth.” In other words, he preached that a moral transformation must precede any real advance. Yet he was not a Christian. An enemy defined Comtism as “Catholicism without Christianity.” Henri Frederic Amiel, Swiss philosopher and critic, whose chief work, the “Journal Intime,” published after his death, obtained for him European reputation, was a valetudinarian. Amiel wrote but little, but all he accomplished has the quality of exquisite sensitiveness. The great Kant was a wretched little creature barely five feet high with a concave chest and a deformed right shoulder; his constitution was of the frailest, though by taking extraordinary precautions he escaped serious illness. VIII ASTRONOMERS AND MATHEMATICIANS Johann Kepler, the great German astronomer, was a contemporary of Tycho Brahe and Galileo with both of whom he was in correspondence. Kepler’s contributions to science were of the utmost importance. It was he who established the two cardinal principles of modern astronomy—the laws of elliptical orbits and of equal areas. He also enunciated important truths relating to gravity. In spite of the backward condition of mechanical knowledge, he attempted to explain the planetary evolutions by a theory of vortices closely resembling that afterwards adopted by Descartes. He also prepared the way for the discovery of the infinitesimal calculus. His literary remains were purchased by Catherine the Second of Russia and were only published during the latter half of the Nineteenth Century. It is impossible to consider without astonishment the colossal amount of work accomplished by Kepler, despite his great physical disabilities. When only four years old an attack of small-pox had left him with crippled hands and eyesight permanently impaired. His constitution, already enfeebled by premature birth, had to withstand successive shocks of illness. Flamstead, the great British astronomer, was obliged to leave school in consequence of a rheumatic affection of the joints. It was to solace his enforced idleness that he took up the study of astronomy. The extent and quality of his performance is almost unbelievable when one considers his severe physical suffering.