After receiving his doctorate in 1897, Pedersen proceeded, as professor at the University of Copenhagen, to enrich language science with an enormous number of books and articles of high originality. Trained in the exacting methodology of the Neogrammarian school of linguistics, he went far beyond its limits to become a participant in, or a critic of, most succeeding schools of linguistic thought, and he also anticipated some new trends. His Celtic researches appeared in many papers, in his monumental Vergleichende Grammatik der keltischen Sprachen, 2 vol. (1909–13; “Comparative Grammar of the Celtic Languages”), and in the Concise Comparative Celtic Grammar (1937), done in collaboration with H. Lewis. About 30 books by Pedersen in Danish, English, French, and German offer authoritative treatments of Albanian, Armenian, Russian, and Indo-European dialects; Lithuanian, Hittite, Tocharian, Czech, and Turkish phonology; the relationship of Indo-European to the Semitic and Finno-Ugric languages; and the origin of runes. A work on the history of linguistic science was reissued under a new title, The Discovery of Language, in 1962.