The article provides a biographical sketch of Theodor Mommsen, a German historian of the Roman republic. The civic courage of Mommsen was as distinctive as his erudition. Mommsen insisted that true history could never be a detached, bloodless inquiry into the past. As a student of Roman law, he learned to understand Rome's history as a story of institutions that had developed over centuries. He won a travelling fellowship to Italy, where he studied thousands of preserved Roman inscriptions.