He regarded the formal definition of papal infallibility as untimely, a conviction which he, with thirteen other bishops, expressed in a letter to the pope, 4 September 1869.

At the session of 13 July 1870, he voted negatively on the question of papal infallibility; but he refused to sign an address in which fifty-five other members of the minority notified the pope of their immediate departure and reiterated their non placet.

He left Rome before the fourth session, giving as his reason the outbreak of the Franco-Prussian war, and declaring his readiness to abide by the decisions of the Council.

As a means of ensuring obedience to the Council, the bishops assembled by him in Fulda, published (1 September) a joint letter, for which Pius IX (20 October) expressed gratitude.

In June, 1873, he excommunicated two priests who had joined the Old Catholics; for this and other administrative acts he was fined and imprisoned for six months (12 March–October, 1874).