A shared interest in the lives of the saints brought him in contact with Alexander Forbes, the learned Anglican bishop, with whom he corresponded at length. De Buck was also a friend of Bishop Félix Dupanloup. These relations were brought about by the reputation for deep learning, integrity, and scientific independence that de Buck's works had earned for him, by his readiness to oblige those who addressed questions to him, and by his earnestness and skill in elucidating the most difficult questions. Grave and direct accusations were made against de Buck and reported to the pope.