Johann Gottlieb Fichte was the son of a ribbon weaver, sent to school by a nobleman who admired his memory for sermons, and made famous overnight when his first book appeared anonymously and was taken for Kant's. He held the chair at Jena, lost it in 1799 in the atheism controversy after publishing an essay identifying God with the moral order of the world, and ended as first elected rector of the new University of Berlin.
The Wissenschaftslehre begins from a dissatisfaction with Kant. If the thing-in-itself is unknowable, Fichte argued, it does no work and should go; and if it goes, the whole system must be derived from the one thing given absolutely, which is the I positing itself. From that act he deduces the not-I, the categories, and the structure of experience. It is idealism carried to its limit, and it is also, in his hands, moral rather than metaphysical: the self is fundamentally activity and striving, the world is the material of duty, and theoretical philosophy exists to underwrite practical philosophy. What sort of philosophy one chooses, he wrote, depends on what sort of person one is.
His politics moved a long way. The early Fichte defended the French Revolution when that was dangerous, argued for freedom of thought against princes, and in the Closed Commercial State of 1800 proposed an economically self-sufficient republic that guarantees every citizen the means of subsistence — an early and thorough statement of the state as guarantor of material right, claimed since by socialists and by autarkists.
Then came Jena and the French occupation of Berlin. The Addresses to the German Nation, delivered in the winter of 1807-08 in a city under French guard, argue that Germany can be reborn only through a total national education forming citizens who will the good spontaneously, and that the Germans are an Urvolk speaking an original language while the Romance peoples speak derived ones. The lectures are the founding document of German cultural nationalism as a political programme; they were quarried enthusiastically in 1914 and after 1933, and the argument over how much of that Fichte licensed has never settled.
Between the two stands his account of recognition — that self-consciousness requires being summoned by another free being — which Hegel took over and made central.