As the teaching of the latter science was discontinued in this academy in 1839, he entered the ecclesiastical seminary at Würzburg and continued his studies there from the autumn of 1839 to that of 1841.
In the first volume of his work, Aus Welt und Kirche, Hettinger gives an account of his student days in Rome.
The Catholic Encyclopedia describes Hettinger and his colleagues Joseph Hergenröther and Denzinger as "a brilliant constellation to which the theological faculty of Würzburg owed the high repute which it enjoyed for many years."
He was called to Rome with Hergenröther in 1868 to assist in the preliminary work of the First Vatican Council, and appointed consultor to the theologico-dogmatic commission.
It was the fruit of time in Italy, and particularly Rome, and of his other vacation trips through various parts of Germany, Austria (especially Tyrol), Switzerland, and France.
His study of Dante inspired the following productions: To the domain of practical theology belong: Lesser writings: Numerous treatises and some longer essays, which were partly preparations for his great works, were published by Hettinger in various reviews: "Katholische Wochenschrift" (Würzburg, 1853–56); "Katholik" (1860–62); "Chilianeum" (Würzburg, 1862–69); "Oesterreichische Vierteljahresschrift für katholische Theologie" (1865); "Historisch-politische Blätter" (1874–90); "Theologisch-praktische Quartalschrift" (Linz, 1881–87, 1889–90).
258–307; and separately, Würzburg, 1870) was written jointly by Hettinger and Hergenröther, the former being the author of the parts concerning dogma, and the latter, of the historico-canonical matter.