In 1842 he earned a doctor of philosophy at the University of Leipzig, and in 1847 he accepted a call to the University of Christiania where he remained for the rest of his life, declining calls to University of Rostock in 1850, to University of Tartu in 1856, and to University of Erlangen-Nuremberg in 1857 and again in 1867. His linguistic ability enabled him speedily to master the Norwegian language, so that he could begin lectures in less than a year. He was made full professor in 1857. In his university work Caspari interpreted various books of the Old and New Testaments and treated Old Testament introduction. His lectures were inspiring, thorough, earnest, and bore evidence of a living Christian faith. In his exegesis and apologetics he followed Ernst Wilhelm Hengstenberg and remained to the end an opponent of modern critical scholarship. But his work and interest were not confined to the Old Testament field. In 1825 a Danish preacher, N. F. S. Grundtvig, propounded peculiar views, viz., that the baptismal formula, the renunciation, the Lord's Prayer, and the words of the Lord's Supper come directly from the Lord, have never been changed, and therefore stand above the Scriptures. The view found adherents in Denmark and Norway, and fear was felt that the formal principle of the Lutheran Church was in danger. Caspari undertook a careful investigation of the questions connected with the baptismal formula, and its history and thus was led on to extensive ecclesiasticopatristic studies. He published a long series of articles and books as the result, most of them in the Norwegian language. In 1862, together with Gisle Johnson, he published a Norwegian translation of the Book of Concord, which was published in 1866, and later in several reprints. He a member of the Central Committee of the Norwegian Bible Society. He assisted in making a new translation of the Old Testament, which was completed for the seventy-fifth anniversary of the Society on 26 May 1891. He was chairman of the Central Committee of the Norwegian mission among the Jews from 1866 to his death in 1892. At the time of his death he was also working on a new translation of the New Testament. He died in Christiania.
Other works
He published an essay upon the Wandering Jew ; a commentary on the first six chapters of Isaiah ; a historical essay on the confession of faith at baptism ; on Abraham's trial and Jacob's wrestling with God ; on Abraham's call and meeting with Melchizedek ; a volume of Bible essays. With Gisle Johnson he established in 1857 the Theologisk Tidskrift for den evangelisk-lutherske Kirke i Norge, of which a volume appeared annually until shortly before Caspari's death. Most of the articles were written by the editors, and in this and other periodicals a large number of Caspari's writings were originally published.
Selected publications
Exegetisches Handbuch zu den Propheten des Alten Bundes
Beiträge zur Einleitung in das Buch Jesaia und zur Geschichte der jesaianischen Zeit
Ueber den syrischephraimitischen Krieg unter Jotham und Ahas
Ueber Micha den Morasthiten und seine prophetische Schrift
Ungedruckte, unbeachtete und wenig beachtete Quellen zur Geschichte des Taufsymbols und der Glaubensregel
Zur Einführung in das Buch Daniel
Alte und neue Quellen zur Geschichte des Taufsymbols und der Glaubensregel ; an edition of Martin of Braga's De correctione rusticorum
Kirchenhistorische Anecdota nebst neuen Ausgaben patristischer und kirchlich-mittelalterlicher Schriften
Eine Augustin fälschlich beigelegte Homilia de sacrilegiis
Briefe, Abhandlungen und Predigten aus den zwei letzten Jahrhunderten des kirchlichen Alterthums und dem Anfang des Mittelalters