Strongly in agreement with the Hegelian tradition, he defended and amplified it in Die gegenwärtige Aufgabe der Philosophie (1852) and Verstehen und Beurteilen (1877).

[1] In these works, he emphasized the identity of the subjective and the objective for consciousness, and the fact that the perception of this unity is peculiar to man.

He is more important, however, as a commentator and scholar, and made valuable contributions to the study of Aristotle.

[1] The work by which he is best known is Geschichte der Logik im Abendlande (4 volumes) (Leipzig: Verlag von S. Hirzel, 1855–1870) (History of Logic in the West).

Christoph von Sigwart, in the preface to the first edition of his Logic, makes special mention of the assistance he obtained from this work.