Christoph Sigwart, the German philosopher and logician, was born and died in Tübingen. He studied philosophy, theology, and mathematics there and taught in Halle from 1852 to 1855, before joining the theological seminar in Tübingen in 1855. He accepted a professorship at Blaubeuren in 1859 and returned to Tübingen as professor of philosophy, a position he held from 1865 to 1903. His doctoral dissertation was on Giovanni Pico della Mirandola. He also wrote on Friedrich Schleiermacher, Benedict de Spinoza, Huldrych Zwingli, and Giordano Bruno, as well as on ethics. His most important work was the two-volume Logik, a comprehensive treatise on the theory of knowledge.

The aim of logic, Sigwart maintained, is normative rather than descriptive. Logic is a regulative science whose aim should be to present a useful methodology for the extension of our knowledge. It is "the ethics rather than the physics of thought" and...