The statement that Christ’s kingdom will have no end in the Nicene-Constantinople Creed of 381 is sometimes interpreted as a rejection of the premillennialism of many of the earlier church fathers such as Papias and Irenaeus. But in reality, this phrase has nothing to do with Revelation 20 and everything to do with the theology of Marcellus of Ancyra. Marcellus was one of the original signers of the Nicene Creed of 325 and an opponent of Arianism. But he held to a form of Logos Christology which taught that God in eternity past was unitarian in person and then became trinitarian for the purpose of creation and redemption. But unlike the other proponents of Logos Christology, such as Eusebius of Caesarea, he believed that God would not be eternally triune, but return to being unitarian in person in eternity future just as he had been in eternity past. He also believed in incarnational sonship which teaches that the Son did not exist as the Son before the incarnation, but only as the Logos. G. L. Prestige describes his theology this way:
“Marcellus’ doctrine appears to have been that the godhead was originally a monad, which developed, of its own nature and character, by a process of active expansion into the triad; the Logos proceeded forth from God by an operative impulse in the beginning of world-creation; at the end of the world, when this operation of the Logos should be completed, His separate existence once more would be merged in God as it was in the beginning. It might be said of this theory that it maintained a Sabellian view of God before the creation began and after the creation should have ceased, and Eusebius attacked it with immense persistence” (God in Patristic Thought, 212).
Because he was one of the original signers of the Nicene Creed, the First Council of Constantinople wanted to distance themselves from him as much as possible. Marcellus’ signing of the Nicene Creed was one of the chief arguments used against it by the semi-Arians. They argued, “How can we affirm the Nicene Creed when this heretic was able to do so? If it was unable to prevent the heresy of Marcellus, it is insufficient as a basis for doctrinal unity.” The Arians had long argued against the Nicene Creed because of its affirmation that Christ is homoousios or of the same nature as the Father. They believed that this would lead to modalism or Sabellianism because if the Son shares the same nature as the Father, then there would be no way to distinguish between the Father and the Son. Marcellus was living proof of this danger and therefore they argued that Nicaea had to be rejected. The inclusion of the statement that Christ’s kingdom will have no end was the orthodox response to this objection by distancing the theology of the First Council of Constantinople from that of Marcellus and ensured that signing the Nicene-Constantinople Creed was in no way an endorsement of the theology of Marcellus. Christ’s kingdom will never end because he will exist for all eternity as a distinct person from the Father rather than being absorbed back into him.