[This article was taken from Appendix C (Orthodoxy, Heterodoxy, Heresy) of our book One God & One Lord.]
In this section, we will provide the reader with an overview of some of the teachings that have been considered heretical by the historic Christian church. There have been many “heretical” positions because the doctrine of the Trinity is so difficult to explain or articulate in a way that will preclude such “misunderstandings.” This is admitted by Trinitarian scholars, such as Thomas Morris  and Adolph Harnack, who writes:
Unfortunately, this Trinitarian theology that is so vital to Christianity is very hard to formulate in any detail without falling into one pitfall or another, as readers of Augustine’s de Trinitate will discover. 
One Unitarian scholar observes that Trinitarians promote their doctrine most successfully when they just state it plainly with no attempt to explain its paradoxes:
One or other among them [Trinitarians] rejects the Trinitarian meaning from each single passage brought in support of it. But this diversity, while it weakens the force of that particular argument, is itself even more fatal to the doctrine. It cannot be so stated that the mass of its supporters will accept the statement. Some dangerous heresy has always been detected, lurking under the disguise of every possible interpretation; and those have uniformly succeeded best who have simply stated the bald dogma, in the most paradoxical form possible, and have left the explanation as a “mystery,” to shift for itself. 
The following are some of the main beliefs that have been condemned as heretical by “orthodoxy” since it was first established. In some cases, we note whether these views are still represented by contemporary groups, or whether scholars mention them as still being a contemporary issue.
Christ was a fully flesh-and-blood human being, not pre-existent or, for most adoptionists, born of a virgin. They teach that Christ was not born the Son of God, but was adopted as such at some point later in his life (his baptism, his resurrection, etc.)
This is the heresy debated at the Council of Constantinople I (381 AD) which asserts that Jesus was not fully human. He was believed to be fully divine and therefore could not at the same time be fully human.
The belief that Jesus was the first of all created beings, pre-existent but eternally subordinate to God, being of different substance from the Father (heterousios). Jehovah’s Witnesses are generally in this category.
The belief that the Son was “like” (homoiousios) the Father but not of one substance (homoousios) with him. The two words being distinguished by a single “i” led to the popular expression, “It makes not an iota of a difference.”
This was the teaching that Jesus only appeared to be a man, but was really some kind of angel or spirit being. The doctrine of the two natures established at the Council of Chalcedon supposedly corrected this error by asserted that Christ was 100 percent man. But as a result of their understanding of the orthodox position that Jesus the man is somehow also “God,” most Christians persist in what J.A.T. Robinson calls a “supranaturalistic” view of Christ that is, in essence, “docetic”:
In fact, popular supranaturalistic Christology has always been dominantly docetic. That is to say, Christ only appeared to be a man or looked like a man: ‘underneath’ he was God. 
This is the view held by the Eastern Orthodox churches, that Jesus was only one person with one nature, a blend of humanity and deity. Hanson suggests that the Jesus portrayed in the Gospel of John “is moving towards Monophysitism. His Jesus is a monophysite figure in the sense that he seems to be a blend of divine and human…where the Transfiguration is taken as an index of Jesus’ real person while on earth.”  Cullman sees this same thinking in the average Roman Catholic, even though the Church has condemned it as heresy:
Despite its official condemnation, Monophysitism still dominates the religious thinking of the average [Roman] Catholic. Jesus and God are often no longer distinguished even by terminology. The question has rightly been raised whether the need for veneration of Mary has not perhaps developed so strongly among the Catholic people just because this confusion has made Jesus himself remote from the believer. 
Cullman’s observation that Jesus and God are not distinguished even in terminology seems to be an accusation that would apply to Trinitarianism in general. The customary distinction is between the “Father” and the “Son,” not between “God” and “Jesus.” The position of the orthodox Church is that Christ has two different natures, with two wills, one human and one “God,” that coexist in him. We believe that Scripture testifies to Christ as the Last Adam, a man like us, having one nature and therefore one will.
This concept is held by those like Jews, Muslims and Unitarians, who believe that God is only one person. Rahner accuses virtually all Christians of this heresy: “…despite their orthodox confessions of the Trinity, Christians are, in their practical lives, almost mere ‘monotheists.’” 
In American Church history, the Protestant majority has remained Trinitarian chiefly by practicing serial monotheism—focusing now on one, now on another member of the Holy Trinity. Apparently this is a practical accommodation to confusing Trinitarian terminology that can be avoided if one does not try to talk about all three persons in one breath.
This is the view held by Nestorius and debated at the Council of Ephesus in 431 AD. This view held that Christ is composed of two separate “persons,” one a “God person,” and the other a “human person.” Nestorianism was condemned and the “orthodox” belief that Christ was one person, both 100 percent God and 100 percent man, was upheld.
Also called “Sabellianism” and “Modalistic Monarchianism”; the view that Christ was actually God the Father in the flesh.
Sabellianism or Modalism
So called because God is thought to have three modes of being rather than existing simultaneously and eternally as three distinct persons. Sabellius taught that the Godhead was a monad, expressing itself in three operations: as Father, in creation; as Son in redemption; as Holy Spirit, in sanctification. The Oneness Pentecostals are criticized for taking this position, because for them Jesus is the Father, the Son and the Holy Spirit. Michael Servetus, in his critique of the Trinity, proposed a semi-Sabellian idea that Christ and the Holy Spirit are merely representative forms of the one Godhead, the Father. Swedish mystic Emanuel Swedenborg also taught a form of this doctrine.
This heresy is committed still by many Trinitarian apologists, when they use the famous analogy of ice, water and steam being “three in one.” But because the same H20 molecules can only be in one form (ice, water or steam) at one time and under the same conditions, the argument is actually Sabellian. Many Christians who advance this analogy to propound the Trinity would be shocked to find that they were falling into a heresy that was long ago condemned.
The view that a spirit being called “Christ” came into the man Jesus at his baptism, and left him again before his crucifixion. Thus, “Jesus” and “Christ” were separate individuals.
This is the view that Jesus is subordinate to God and therefore not eternally co-equal. Eastern Orthodox Churches teach that Christ has a subordinate rank to the Father while still maintaining his deity. More extreme forms forbid “prayer” to Jesus Christ as inappropriate and even devilish.
Tri-theism or Polytheism
The three persons of the Godhead are considered as three separate “Gods,” or are spoken of as “three” more than they are spoken of as “one.” They are said to be united in one substance, so they are technically “one God.” “Social Trinitarianism,” especially popular today, emphasizes the fellowship and interaction of each of the three divine persons to the point that critics say monotheism is compromised. Says Gunton:
One danger of the concept of communion—and especially of a “social” analogy of the trinity—is of a form of tri-theism which appears to relate the three persons in such a way as to suggest that they have distinct wills…we may accept the principle, so influential in the West in particular, that the acts of the triune God in the world are undivided. But this principle, like so many others—including the homoousion—can be the source of confusion unless it is carefully qualified…The concepts of homousios and perichoresis [that each of the persons “envelops the other”], are vital devices to ensure that trinitarian language does not lapse into tritheism. 
Most Trinitarian Christians are actually practicing “Tri-theists.” They think of God, Christ and “the Holy Spirit” as separate beings, not as “one God.” This is undoubtedly due to the impossibility of holding both ideas in the mind simultaneously. Either God is “one” or He is “three.” To say He is truly both defies logic and common sense and cannot be practically grasped or applied.
1. See the quote in Chapter 20 by Morris from The Logic of God Incarnate (Cornell University Press, Ithaca, NY, 1986), pp. 207 and 208. Back to top
2. Adolf Harnack, Lehrbuch der Dogmengeschichte (The History of Dogma), (Mohr, Tubingen, 1909), II, p. 295. Back to top
3. Joseph H. Allen, Ten Discourses on Orthodoxy (Wm. Crosby and H.P Nichols, Boston, 1849), pp. 58 and 59. Back to top
4. Robinson, op. cit., Honest to God., p. 66. Back to top
5. Hanson, op. cit., Prophetic, p. 366. Back to top
6. Oscar Cullman, The Christology of the New Testament (Westminster Press, Philadelphia, 1963), p. 306. Back to top
7. Rahner, op. cit., The Trinity, p.10. Back to top
8. Gunton, op. cit., Promise, p. 198. Back to top