Gustav Theodor Fechner was born on April 19, 1801, at Gross-Särchen in what is now Silesia, then under the Elector of Saxony. He studied at Leipzig, and was appointed professor of Physics at the University there, in 1834. He conducted several scientific journals, wrote text-books, translated Biot's _Physics_ (4 vols.) Thénard's _Chemistry_ (6 vols.) and a work on cerebral pathology; also edited an eight-volume _Encyclopædia_ of which he wrote about a third himself, lectured, and made researches in electro-magnetism which injured his eyesight. His chief scientific work, _Elements of Psycho-Physics_, was published in 1859, additions being made in 1877 and 1882. "Fechner's Law", the fundamental law of psychophysics (that sensation varies in the ratio of the logarithm of impression) is now an internationally current term. Men like Paulsen and Wundt do not hesitate to call Fechner master. His chief philosophical work is _Zend-Avesta_ (3 vols.) published in 1851, and rearranged and condensed in _Die Tagesansicht gegenüber der Nachtansicht_ (1879); but he published also many subsidiary volumes. Only one of his works has appeared in English--the small volume on _Life After Death_--and even this had to be brought out by an American publisher! Yet Fechner is, as Professor William James said, "a philosopher in the great sense ... little known as yet to English readers, but destined, I am persuaded, to wield more and more influence as time goes on". (_A Pluralistic Universe_, pp. 135, 149.) The prophecy is already beginning to come true. Fechner always begins with the known and indisputable, arguing thence to the unknown. His method is thus analogical and scientific. It is the only method that a scientific generation will tolerate. Its results may be disputed, but so can the results of science. Even mathematics gives us no certainties, for something must always be taken for granted. In philosophising by analogy, we do at least keep in close touch with experience; we do not evaporate the world into an "unearthly ballet of bloodless categories". And if the analogies point mostly one way, with only weak ones pointing the other, the result may be at least acceptable as a working hypothesis, even if not "demonstrable".