Hefele was born at Unterkochen in Württemberg and was educated at Tübingen, where in 1839 he became professor-ordinary of Church history and patristics in the Roman Catholic faculty of theology,[1] while collaborating along with William Robinson Clark to his major work.
[1] Hefele's theological opinions inclined towards the more liberal school in the Roman Catholic Church, but he nevertheless received considerable signs of favour from its authorities, and was a member of the commission that made preparations for the Vatican Council of 1870.
On the eve of that council he published at Naples his Causa Honorii Papae, which aimed at demonstrating the moral and historical impossibility of papal infallibility.
He took rather a prominent part in the discussions at the council, associating himself with Félix Dupanloup and with Georges Darboy, archbishop of Paris, in his opposition to the doctrine of Infallibility, and supporting their arguments from his vast knowledge of ecclesiastical history.
He was absent from the important sitting of June 18, 1870, and did not send in his submission to the decrees until 1871, when he explained in a pastoral letter that the dogma "referred only to doctrine given forth ex cathedra, and therein to the definitions proper only, but not to its proofs or explanations".