My own reasons for not becoming Roman Catholic have not changed. It was precisely the problem of doctrinal development that I found unsatisfactory. I believe that J. B. Mozley’s The Theory of Development provides the decisive critique of [John Henry] Newman on development of doctrine. Mozley argues that Newman commits a logical fallacy of amphiboly by not distinguishing between two different kinds of development. Newman is correct that there is genuine development in the early church....the “development” of incarnational and Trinitarian doctrine that takes place at Nicea, Chalcedon, etc., is really simply the necessary logical unfolding of what is already clearly present in the New Testament. If Jesus is fully God, then he must “of the same substance” as God. If the Father, Son, and Holy Spirit are equally God, and yet there is only one God, then God must be three persons in one nature....
Mozley speaks of this kind of development in terms of what I will call “Development 1.” Development 1 adds nothing to the original content of faith, but rather brings out its necessary implications. Mozley says that Aquinas is doing precisely this kind of development in his discussion of the incarnation in the Summa Theologiae.
There is another kind of development, however, which I will call “Development 2.” Development 2 is genuinely new development that is not simply the necessary articulation of what is said explicitly in the Scriptures.
Classic examples of Development 2 would include the differences between the doctrine of the theotokos and the dogmas of the immaculate conception or the assumption of the Blessed Virgin Mary. In the former, Marian dogma is not actually saying something about Mary, but rather something about Christ. If Jesus Christ is truly God, and Mary is his mother, then Mary is truly the Mother of God (theotokos). She gives birth, however, to Jesus’ humanity, not his eternal person, which has always existed and is generated eternally by the Father. The doctrine of the theotokos is a necessary implication of the incarnation of God in Christ, which is clearly taught in the New Testament. However, the dogmas of the immaculate conception and the assumption are not taught in Scripture, either implicitly or explicitly. They are entirely new developments.
The same would be true, of course, for the doctrine of the papacy. The New Testament says much about the role of Simon Peter as a leader of the apostles. It does not say anything explicit, however, about the bishop of Rome being the successor to Peter. The Eastern fathers, e.g., Cyprian, interpret the Petrine passages that Rome has applied to the papacy as applying to all bishops.
C.S. Lewis, also in his essay "Christian Reunion," cited this in his decision not to become a Roman Catholic: "to accept your Church means not to accept a given body of doctrine but to accept in advance any doctrine that your Church hereafter produces."
[Edited to correct the spelling of "amphiboly" and provide the link to its definition: Linguistically, an amphiboly is an ambiguity which results from ambiguous grammar, as opposed to one that results from the ambiguity of words or phrases—that is, Equivocation. The fallacy of Amphiboly occurs when a bad argument trades upon grammatical ambiguity to create an illusion of cogency. Amphibolies are often linguistic boobytraps, but less frequently do they occur in fallacious arguments.]