From the period of the writing of the New Testament onward, the extant documents of the early church demonstrate a commitment to the fundamentals of what was eventually defined in the creeds as the doctrine of the Trinity, the unity of the Godhead and the divinity of the Father, Son and Holy Spirit. As time went on, various heresies and heterodox opinions developed within the church, or permeated it from without, only to be rejected. Opposition to the orthodox doctrine of the Trinity took various forms, some subtly different, others barely recognisable as having any connection with Christianity. Whilst it is not unreasonable to assume that there have nearly always been individuals and groups within the history of the church who rejected the divinity of the Son and the Holy Spirit, the challenges to Trinitarian orthodoxy have been quite diverse, and remain so today.
Christadelphians are one denomination which rejects the doctrine of the Trinity. They regard Jesus Christ as the Son of God by miraculous conception of the Holy Spirit but in all other respects a human being who did not pre-exist his conception and was not intrinsically divine but was later rewarded with Lordship. Christadelphians call their doctrine of God’s work in the man Christ Jesus “God Manifestation;” the divinity manifest in Christ was that of the Father, not a pre-existent Son.
Christadelphians believe themselves to be a/the modern revival of the original and true apostolic faith, and reject a number of orthodox doctrines. The “Truth” in its entirety was, they believe, only rediscovered in the mid 1800s by John Thomas, who founded the Christadelphians. This occurred not by any additional revelation, but simply by reading the Bible more carefully and objectively than anyone else had in the history of the church. Nevertheless, Christadelphians generally believe that God did not let “the Truth” disappear completely in those 1850 or so years, but throughout most of Christian history preserved a remnant from generation to generation who held to some, most or perhaps on rare occasions, all of the “Truth.”
Alan Eyre states, “Today the Christadelphian community… is the inheritor of a noble tradition, by which elements of the Truth were from century to century hammered out on the anvil of controversy, affliction and even anguish.” Fred Pearce observes, “It is a matter of great encouragement to us, whose religious views are regarded as unorthodox by our contemporaries, to find that in a number of cases where major doctrines are concerned, these early believers had come to the same conclusions as ourselves. And how should it be otherwise, for we have sought to do what they did — go back to the Scriptures alone in our search for truth.” 
The thesis of this and subsequent blogs in the series is that Christadelphians inhabit a doctrinal island, distinct from other anti-trinitarian groups. I will endeavour to demonstrate that non-trinitarians through the ages actually did NOT believe what Christadelphians believe, in fact some supposedly “non-trinitarians” appealed to by Christadelphians were actually quite orthodox in their understanding of the Godhead. Furthermore, some non-trinitarian positions were so at odds with Christadelphian beliefs that they would never be in “fellowship” with them, which makes them strange bedfellows as sympathisers, let alone “predecessors.” Christadelphians are unique in their understanding of the Godhead, the person and work of Christ and particularly with respect to their view of “God manifestation,” and their teachings should be addressed on their own terms.
The first non-trinitarian group we will examine are the second and third century adoptionists. The definition is multi-faceted, but essentially what the adoptionists held in common was that Jesus Christ was Son of God by adoption, not by essence or by conception. In a previous blog I discussed one form of Monarchianism (a mon-arch is a sole ruler), that of Modalism, and compared it with the Christadelphian doctrine of God manifestation. Modalism taught that the one God was manifest at different times in salvation history as Father, Son and Spirit. Whilst this preserves the unity of the Godhead, it erases the distinctiveness between Father, Son and Spirit which is so evident in Scripture and leads to the assertion that the Father himself suffered and died on the cross in the person of Christ. Whilst God-manifestation has some affinities with modalism, it is essentially different.
Another form of Monarchianism was dynamic monarchianism, or adoptionism, which taught that Jesus Christ was born human to Joseph and Mary and only became divine when adopted by God at his baptism. The earliest extant text containing adoptionist ideas is the second century Shepherd of Hermas, whose somewhat confused theology is an amalgam of binitarianism and adoptionism. The Lord is presented as a virtuous man who was indwelt by the pre-existant Spirit of God and adopted as God’s Son due to his meritorious cooperation with the indwelling Spirit  . There are also strong traces of second temple Judaistic angelology in this work, whereby the Son of God is essentially equated with the archangel Michael.
Around 190 AD a Byzantine named Theodotus taught that Jesus, born of a virgin, lived as an ordinary, albeit virtuous, man until his baptism. The Spirit, or Christ, descended on Jesus at his baptism (Matt 3:16–17) and enabled him to work miracles, without making him divine. This doctrine was formally rejected as heretical. Other adoptionists determined that Jesus became divine at his resurrection. Either way, the Son as a person did not pre-exist his birth. The dynamic monarchians were concerned that an emphasis on the intrinsic divinity of Christ was really a statement of ditheism; that orthodoxy was promulgating two Gods not one and that true apostolic teaching (which they of course claimed) had been tampered with.
In the first half of the third century, Paul of Samosata taught that the self-subsistent Word was not a person or substance but God’s commandment, which indwelt Christ and thus made Christ a conduit for God’s word. He taught that Jesus was a man who kept himself sinless and thereby achieved union with God. Paul was excommunicated in 268 and thereafter his influence was alleged to underlie some of the later Christological heresies such as Nestorianism.
A problem underlying many if not most of the early heresies was Greek dualistic philosophy. The Greeks regarded matter and the body and created things as intrinsically evil, in contrast to divine and spiritual things, which were good. Like oil and water, these could not mix. They therefore had a problem with the incarnation and the resurrection. How could the ultimate Divinity sully his hands by creating matter? How could God enter the human world? How could the divine and human be combined in a man in any real sense? And why would it be thought reasonable to resurrect bodies of matter for the soul to indwell? This difficulty manifested in diverse ways, sometimes downplaying Christ’s divinity, sometimes his humanity and sometimes the union of the two. The Docetists taught that the divine Christ only seemed human but could not have really died on the cross; he only appeared to have suffered. This is probably the error refuted in 2 John 1:7. Adoptionism was another solution; the divine Christ indwelt a worthy man who was declared to be God’s Son but was not intrinsically divine. In some versions of adoptionist and Gnostic theology the “Christ” or Spirit left Jesus prior to his suffering and death so it was only the fleshly man Jesus who died.
Nestorius (386-450) was accused of teaching an adoptionist Christology and an incomplete union between the divine and human natures. It is difficult to no whether Nestorius himself believed all that has been attributed to him, but certainly Nestorianism’s separation of the divine and human in Christ could be construed as akin to adoptionism or at least some form of dualism.
Dualism was also a major tenet of the various forms of Gnosticism, which had their heyday in the second through fourth centuries. Gnosticism was very diverse and permeated not only Christianity but Judaism and pagan religions as well. The various versions of Gnosticism taught that from the supreme divine being emanated a number of aeons on a descending scale of divinity and that one of the lower, corrupted emanations was the evil demiurge who created matter. Entrapped souls can only escape matter by attainment of true gnosis (knowledge) and ultimately ascend back to the pleroma, or fullness. There are various saviour figures within Gnostic systems; this role may be taken by Jesus, sometimes as a divine figure who became incarnate. In other versions Jesus is a mere human who attained divinity through gnosis and taught his disciples the secret knowledge.
Although the Greek distaste for blending the divine and human doubtless undergirded some adoptionist Christologies, adoptionism has also been ascribed to some Jewish Christian movements. The Ebionites are typically described as Judaizers, however Epiphanius of Salamis, in his compendium of heresies stated that the Ebionites believed Christ to be an archangel incarnated in Jesus and adopted as the Son of God. Not all scholars accept this account as accurate, however Goulder has suggested that the odd combination of Judaizing and Docetic heresies attacked by Ignatius in the early second century could refer to a single group, the Ebionites.
There was no one form of adoptionism and it can readily be countered with such scriptures as Matt 1:18–23; Luke 1:30–35; John 1:1–2, 14; 17:5; Col 1:15–17; Heb 1:3, 8, 10. It never gained much headway and tended to be quickly identified as heresy and condemned by the early church. It made a couple of notable curtain calls, particularly in the eighth century in Muslim-ruled Spain under Elipandus of Toledo and in twelfth century France as Peter Abelard’s “neo-adoptionism.” Qualified forms of adoptionism were also put forward by later scholars.
Christadelphian apologist Thomas Gaston makes reference to possessionist Christologies in his review of early church documents . He allows that the second and third century writers probably believed in a pre-existent Logos which indwelt Christ but ascribes proto-Trinitarian references (which he believes are genuinely scant) to Platonist influence. Gaston hints that non-trinitarianism was more common than the extant documents suggest; “The works that have been preserved are preserved because they resemble orthodoxy closely enough to pass muster. The works of non-Trinitarians were not preserved and we are reliant on brief references as witness to their existence.” The argument that “only the winners write history” has also been used by proponents of Gnostic, “DaVinci Code” and feminist interpretions of early Christian history, accusing the early church of erasing most of the evidence of non-orthodox beliefs. This of course is an argument from silence and presupposes a curious providence in God’s activity in his fledgling church. The non-trinitarian writers to whom Gaston does refer as evidence for his suppressionist theory are the likes of Cerinthus, Marcion, Valentinus and Basilides  who would not find any mutuality with Christadelphian beliefs.
So then, are Christadelphians adoptionists? On face value, there seems to be some common ground. Robert Roberts described Jesus as “a divine manifestation — an embodiment of the Deity in flesh — Emmanuel, God with us… The spirit descended upon him in bodily shape at his baptism in the Jordan, and took possession of him. This was the anointing which constituted him Christ (or the anointed) and which gave him the superhuman powers of which he showed himself possessed… Before his anointing, he was simply the ‘body prepared’ for the divine manifestation that was to take place through him… After the Spirit’s descent upon him, he was the full manifestation of God in the flesh.” 
This sounds very like Theodotus’ adoptionism and more recent Christadelphian writers have stepped back from Roberts’ expressed view. Elsewhere in the same context Roberts makes it clear that Jesus was the Son of God from the moment of his conception, that “God was in Christ” (2 Cor 5:19) applies to the tabernacling of the Father in Christ by the Spirit, and his exaltation and glorification occurred post-resurrection. At this time “his human nature was swallowed up in the divine; the flesh changed to spirit.”
Christadelphian expositor Alfred Nicholls asserts that “the reverence accorded the risen Lord is that which formerly belonged to the LORD alone but has now become Christ’s by Divine gift . Christadelphians ascribe divinity to Christ, but only as something derived and bestowed, never as something intrinsically his. This exaltation and glorification is always presented by Christadelphians as having occurred when Christ was raised and ascended to the right hand of the Father. In this sense his full “adoption” of divinity occurs post-resurrection rather than at baptism, in accordance with some adoptionist beliefs. But they are always adamant that Christ’s Sonship began at his conception; as Harry Tennant states; “No other child has ever been truly ‘Immanuel;’ no other, ‘the Word made flesh;’ and none, ‘the holy one.’ Jesus is not mere man and Christadelphians have never believed that. We believe that he is truly and uniquely the Son of God. [ 91]
Nevertheless, in common with Paul of Samosata and others, Christadelphians believe that Jesus’ exaltation and granting of the “Name above every name” was a reward for his works, his faithful life and obedience unto death.  That this sets a precedent for a works-based, imitating-Christ view of salvation has been discussed elsewhere. Christadelphians also refer to the same texts as adoptionists in supporting their belief in Christ’s derived and bestowed divinity; Acts 2:22, 36;17:31; Rom 1:4. By interpreting these passages in an adoptionist sense without regard to wider context, and interpreting all of the scriptural evidence for Christ’s pre-existence and divinity metaphorically, they believe they have proved their case. But their case is not the adoptionist case, if there truly ever was a single common “adoptionism.” Christadelphians deny being adoptionists, and rightly so. Adoptionists believed Christ’s Sonship was bestowed; Christadelphians believe Christ was God’s Son from his conception, anointed with the Spirit at his baptism and exalted to a secondary, derived divine status at his resurrection and ascension. Nevertheless, Christadelphians will side with adoptionists to “refute” those who believe in the pre-existence of the divine Son, but conversely side with passages that teach a more intrinsic divinity or “more-than-just-human” emphasis when actually “refuting” the label of adoptionist or liberal unitarian. They will claim adoptionists, not necessarily as predecessors, but at least colleagues in defence of a non-trinitarian stance. The Christadelphian position draws to varying extents on adoptionism, but cannot be termed adoptionist and would doubtless find no grounds for “fellowship” with any who historically espoused adoptionism.
- Christadelphian Statement of Faith, articles 1, 2, 10, 13 http://www.christadelphia.org/basf.htm Reg Carr, ed. The Testimony Handbook of Bible Principles (King’s Lynn: The Testimony, 2010) 53-56
- Alan Eyre, The Protesters (Birmingham: The Christadelphian, 1975), 8.
- Fred Pearce, preface to Eyre, Protesters.
- “The Shepherd of Hermas,” in Michael Holmes, ed. The Apostolic Fathers: Greek Texts and English Translations, rev ed. (Grand Rapids: Baker, 1999) Parable 5.6: 59, p 437.
- Goulder, Michael D. “Ignatius’ Docetists,” Vigilae Christianae 53(1): 1999, 16-30.
- Thomas Gaston, “After the Apostles,” in Thomas E. Gaston, ed. One God, the Father. (East Boldon: Willow, 2013) p122-134.
- Cerinthus was probably a Gnostic with Ebionite or Judaising ideas who taught a hedonistic earthly millenium. Marcion was anti-Jewish and rejected the Old Testament and portions of the New which had perceived Jewish biases. Valentinus and Basilides were Gnostics.
- Robert Roberts, Christendom Astray from the Bible (repr. South Aiustralia: Logos, 1984), 160, italics his.
- Alfred Nicholls, The Name that is Above Every Name (Birmingham: The Christadelphian, 1983), 67
- Harry Tennant, The Christadelphians: What they Believe and Preach (Birmingham: The Christadelphian, 1998), 100-101