It was to this tendency to inquire into and seek to fathom divine mysteries that the controversy about transubstantiation was due. That controversy came into being a full generation after the death of Alcuin; and one of the most prominent opponents of any approach to a materialistic view of the manner of the Real Presence was a pupil of Alcuin’s, Rabanus Maurus, Archbishop of Mainz. The heresy which reached such dimensions as to call Alcuin back from England to France was the heresy known as Adoptionism. It became prominent in the same manner, from the same tendency to pry into the divine secrets of operation, as did the theory of transubstantiation. The point was, how exactly did the human nature of the Son come into union with the divine nature? The answer given by Felix, Bishop of Urgel in Catalonia, was this—by adoption. Hence he and his followers were called Adoptionists. The term Adoption had been applied to the Incarnation by some early Fathers, and indeed in the Spanish Liturgy, which Felix naturally used. It was used probably as equivalent to assumption—He took upon Him—that is, assumed—our flesh. This use of the word Adoption in their liturgy led Felix and his followers to take a large step beyond the equivalence to assumption. They carried it to its full meaning in ordinary affairs, and declared that the divine nature of the Second Person of the Trinity adopted the human nature into sonship, as Son. The so-called Athanasian Creed has in our English form, “by taking the manhood into God.” In the original Latin the word “assumption” is used, _assumptione humanitatis in Deum_.[167] Catalonia was at that time a part of Karl’s dominions, and therefore he could operate upon Felix. But Elipandus, who supported Felix, was bishop of Toledo and primate of Spain under the Mohammedan dominion, and thus was beyond the reach of Karl. He was a man who, in his letters at least, used very abusive language. The Adoptionists held that it was a confusion of the two natures in Christ to say that Christ was proper and real Son of God not only in his Godhead but in His whole Person. The highest that could befall humanity, they maintained, was to be adopted into sonship with God; therefore Christ’s humanity is adopted into sonship. This adoption had three stages they said; the first at the moment of conception, the second at His baptism, the final stage at His resurrection. The Adoptionists professed to deny that they were Nestorians, that is, that they divided Christ into two Persons; but it was urged against them that if they did not divide Christ into two persons, their theory did, when it was pressed to its necessary consequence. That is the history of the origin of many of the heresies.