Jahn, Johann a distinguished German Roman Catholic theologian and Orientalist, was born at Taswitz, in Moravia, June 18, 1750. He studied at the Gymnasium of Znaym, the University of Olmütz; and the Rom. Cath. Theological Seminary of Bruck, entered the Church, and was for some time a priest at Mislitz. In 1782 he received the doctorate from OlmUtz, and, after having filled with great distinction the position of professor of Oriental languages and Biblical hermeneutics at Bruck, he was, in 1789, called to the University of Vienna as professor of the Oriental languages, dogmatics, and Biblical archaeology. At this high school he labored successfully for seventeen years, amid suspicions and petty persecutions from the court of Rome which pained his ingenuous spirit. Some words in the preface of his Einleit. in, d. Gött. Bucher d. alten Bundes (Vienna, 1703, 1802, 1803, 2 vols. 8vo); the assertion that the books of Job, Jonah, Judith, and Tobit are didactic poems; and that the demoniacs in the N.T. were possessed with dangerous diseases, not with the devil, were made charges against him. In 1792 complaints of his unsoundness were laid before the emperor Francis II by cardinal Migazzi, which resulted in the appointment of a special commission to examine the charges. Although it was decided that Jahn's views were not heterodox, they cautioned him to be more careful in. the future in expressing opinions likely to lead to interpretations contrary to the dogmas of the Church, and even suggested a change of the obnoxious passages (comp. Henke, Achiuf. d. neueste Kirchengeschichte, 2, 51 sq.; P. J. S. Huth, Versuch einer Kirchengesch. d. 18ten Jahrh. 2, 375, 376). Though he honestly and willingly submitted, his detractors continued their machinations till he was (in 1806) removed from the congenial duties of an office to which he had dedicated his life, and was made, merely, of course, to prevent scandal which might have resulted from a deprivation of all dignity, canon or Domherr in the metropolitan church of St. Stephen. Even before he was compelled to resign his professorship, two of his books, Introductio in libros sacros Veteris Testamenti in compendium redacta (Vienna, 1804), and Archaeologica Biblica in compendium redacta (Vienna, 1805), which were then very popular among the university students, were condemned and placed on the Index, without their author being heard in his defense. Jahn died Aug. 16, 1816. Besides the works which we have had occasion to cite, and a series of grammars and chrestomathies on the Hebrew, Syriac, Arabic, and Chaldee languages, he wrote, Biblische Archäologie (Vienna, 1797-1805, 5 vols.; vols. 1 and 2, 2nd edition, 1817-1825): — Lexicon Arabico Latinuns, Chrestonathice Arabicae accomodatum (Vien. 1802): this work was considered the best of its kind until the publication of a similar production by Sylvester de Sacy: — Biblia Hebraica digessit, et graviores lectionum varietates adjecit (Vien. 1806, 4 vols. royal 8vo): Enchiridion Hermeneuticae generclis tabularum, etc. (Vienna, 1812; nwith an Appendix hermeneut., s. exercitationes exegeticce, Vienna, 1813): — Vatcinia Prophetarum de Jesu Messit, commentarius criticus in libros propheticos Veterie Testamenti (Vien. 1815), etc. Sometime after his death appeared Nacchtrie zu Jahn's theologischen Werken, published from his MSS. (Tübingen, 1821), which contained six interesting dissertations on various Biblical subjects, and with them some letters of Jahn's, giving a clew to the motives of the persecutions directed against him. Jahn's memory deserves to be cherished by all true lovers of Oriental scholarship. He furnished textbooks for the study of those languages superior to any of his time, and, although they are at present obsolete, he certainly aided modern scholarship by furnishing superior tools. As a theological writer he was clear and methodical, and his numerous works, of which several enjoy an English dress, "diffused a knowledge of Biblical subjects in places and circles where the books of Protestants would scarcely have been received. The latter, however, have appreciated his writings fully as much as Roman Catholics. He was not profound in any one thing, because he scattered his energies over so wide a field; but he was a most useful author, and one of his books (the Archaeology) is still the largest and best on the subjects of which it treats." As a theologian of the Romish Church he was certainly exceedingly liberal, so much so that Hengstenberg (on the Pentateuch) rather finds fault with him. See Felder, Gelehrt. Lex. d. Kathol. Geistlichkeit, 1, 337; H. Doring, D. gelehrten Theologen Deutschlands 2, 7 sq.; Meusel, Gelehrt. Deutschlands (5th ed.), 3:510; 10:13; 11:994; 14:255; 18:254; 23:18; Ersch u. Gruber, Allg. Encyk.; Kitto, Bibl. Cyclop. s.v.; Werner, Gesch. d. Kathol. Theol. p. 273 sq.