Since his sojourn in Strasbourg, Görres had studied the mystic testimonies of various epochs. He went into the mystical writers of the Middle Ages such as María de Ágreda as well as observing, partly in person, the ecstatic young women of his time (Maria von Mörl, and others), and strove to comprehend more thoroughly the nature of Christian mysticism. His "Christliche Mystik" ("On christian mysticism", 4 vols., 1836–1842; 2nd ed., 5 vols., 1879) gave a series of biographies of the saints, together with an exposition of Roman Catholic mysticism. But his most celebrated ultramontane work was a polemical one. Its occasion was the deposition and imprisonment by the Prussian government of the archbishop Clement Wenceslaus reportedly due to his refusal to sanction in certain instances the marriages of Protestants and Roman Catholics.