In 1842 Hergenröther completed with notable success his gymnasium course in his native town, and entered the University of Würzburg to take up a two-year course of philosophical studies, to which he added certain branches of theology.

Bishop von Stahl took an interest in him, and in 1844 sent him to the Collegium Germanicum et Hungaricum at Rome, whither he had already sent Heinrich Joseph Dominicus Denzinger and Franz Hettinger.

In 1849 he stood successfully for the degree of doctor of theology before the University of Munich, and offered as his dissertation a treatise on the Trinitarian teaching of St. Gregory Nazianzen (Die Lehre von der göttlichen Dreieinigkeit nach d. heil.

Following ancient usage, he justified the confidence of the university by a printed thesis (Habilitationschrift) on the later Protestant theories of the origins of the Catholic Church (De catholicæ ecclesiæ primordiis recentiorum Protestantium systemata expenduntur, Ratisbon, 1851).

In 1852 he was called to Würzburg, as professor extraordinary of canon law and church history; after three years (1855) he was promoted to the full possession of that chair.

When Aloys Pichler's work on the history of the separation of the Eastern and Western Churches appeared (Munich, 1864), Hergenröther was prepared to criticize it in the most thorough manner, which he did in a series of studies in a Würzburg theological periodical, the "Chilianeum" (1864–65), and in the "Archiv.

In this monumental work it is difficult to say whether the palm belongs to the author's extensive knowledge of all the manuscript material, to his profound erudition, or to his calm objective attitude.

While professor of canon law at Würzburg, Hergenröther published several important historico-canonical essays on such subjects as early ecclesiastical reordinations (Ester, Vierteljahrsch.

Among his historico-apologetic essays are his treatises on the errors condemned by the Holy See in the Encyclical (Syllabus) of 8 December 1864 (in the Chilianeum, 1865), the veneration of the Blessed Virgin in the first ten centuries of the Christian Era (Münster, 1870).

For the Fulda meeting of the Prussian bishops (1870) he prepared an exhaustive historical study on the spoliation of the Papal States, in which he developed at length the arguments for the temporal power of the papacy.

At Munich he gained the reputation of being one of the most learned theologians on the Ultramontane side of the Infallibility question, which had begun to be discussed; and in 1868 he was sent to Rome to arrange the proceedings of the Vatican Council.

His knowledge of ecclesiastical history, canon law, and Catholic dogma made him a valuable co-labourer in the many careful and detailed preliminary meetings of the council commission.

In the meantime he prepared, with Hettinger, and published in the "Chilianeum" (1869) a memorial of the theological faculty of Würzburg in reply to five questions, submitted by the Bavarian Government, concerning the approaching council.

He also published (Der Katholik, 1871) another outlined memorial concerning the Vatican Council, in reply to eleven questions submitted by the Bavarian Minister of Worship to the theological and law faculties of Würzburg.

In 1871 he published the solid study "Das unfehlbare Lehrant des Papstes" [The Infallible Magisterium (teaching office) of the pope, Passau, 1871].

When it was proposed to bring out a new edition of the "Kirchenlexikon" of Wetzer and Welte, Hergenröther was naturally suggested as the savant most capable of executing this gigantic task.

He accepted it, but was compelled to abandon it when scarcely begun; his elevation to the dignity of cardinal with the obligation of a Roman residence, left him no freedom for the enterprise.

Hergenröther's works in the departments of church history and canon law, and his firm attitude on the great ecclesiastical questions of the day, won for him the confidence of all the bishops and Catholic scholars of Germany.

When Leo XIII determined to open the Vatican Archives to the scholars of the world, he found in him the savant to whom he might safely entrust the practical execution of this generous act.

He undertook, moreover, to edit the official correspondence (Regesta) of Leo X, a rather thankless task, and one of great difficulty, because of the exceedingly bad handwriting of that day.

A small part of the second volume was brought out (Freiburg, 1891) by his brother and fellow-editor, since which time the publication has ceased by reason of the latter's return to Würzburg as canon capitular of the cathedral.

Cardinal Hergenröther undertook another work of the most exacting nature, the continuation of Karl Joseph von Hefele's "History of the Councils", two volumes of which he published before his death (vol.

In 1870 he wrote Anti-Janus, an answer to The Pope and the Council, by Janus (Ignaz von Döllinger and Johann Friedrich), which made a great sensation at the time.

His portrait was apparently painted by the Swiss-born American artist Adolfo Müller-Ury (1862-1947) during the two years he spent studying in Italy 1882-1884, and was probably signed Ad.