Adolf von Harnock asserted the famous paradigm that early Christianity was corrupted by Greek philosophy. He pointed to the Gnostics as the extreme form of that corruption but asserted that Christianity as a whole was tainted. The way he described the effects of Plato on Christianity would have been (and indeed was) appealing to Mormons. “The Greek spirit” merged with Christianity in the 2nd century “the original enthusiasm, in the large sense of the word, evaporated, and the religion of law and form at once arises.” “The living faith seems to be transformed into a creed to be believed; devotion to Christ, into Christology … prophecy, into technical exegesis and theological learning; the ministers of the Spirit, into clerics; the brothers, into laymen in a state of tutelage, miracles and miraculous cures disappear altogether.” In Karen King’s summary, “Hellenism transformed the Gospel into dogma.” And though the Orthodox rejected the Gnostics, the struggle compelled the Christians to become dogmatic. “We may almost say that the vanquished imposed their terms upon the victor.” 
Some of this ought to sound familiar, and I understand that Matt B. is working on how this narrative was adopted by turn-of-the-century Mormon thinkers.
Yet, I argue here that while adopting von Harnock’s models was understandable, it was incorrect from a Latter-day Saint perspective. Simply put, throughout the history of Christianity, the more Christians were into Plato, the more Mormon they look. Furthermore, research since von Harnock on the Gnostics now call into question the old designation of them being Platonic Christians. The Gnostic belief that the world was created by the evil God is not found in Plato (Plato’s Demiurge creator is good). It was Plotinus (the founder of Neoplatonsism) that denounced the Gnostics for their overly negative view of creation and it was this denunciation that turned Augustine away from Manicheanism (a later form of Gnosticism) to orthodox Christianity. While there are Platonic themes in Gnosticism, only the themes that are in accord with Mormonism can be found in Platonism (like preexistance); evil creation is not Platonic.
Thus we see a number of Mormon ideas in the earliest Christian Platonists like Clement of Alexandria and Origen. Says E. R. Dodds,
The notion that a human being might become a god or daemon after death had of course long been familiar: it is often asserted on pagan tombstones of the Hellenistic and roman periods. But that a man should become a god in his lifetime, ‘a god walking about in the flesh’, as Clement puts it, must seems to us rather odd, if we leave aside the conventions of Hellenistic and Roman ruler-cult. Yet we find this language repeatedly used not only by pagans like Plotinus, Porphyry and the Hermetists, but by Irenaeus and Clement, Origen and Gregory of Nyssa.
God was not as remote and different to pagans, explains Dodds. “Hence the favourite saying that ‘Man is a mortal god, and god is an immortal man.’” 
Says Andrew Louth,
Central to Platonism is its conviction of man’s essentially spiritual nature … the belief of his kinship with the divine. But, for Christianity, man is a creature; he is not ultimately God’s kin, but created out of nothing by God and only sustained in being by dependence on His will. There is an ontological gulf between God as his creation, a real difference of being. Only in Christ, in whom divine and human natures are united, do we find One who is of one substance with the Father. At this point Christianity and Platonism are irreconcilable. 
Yet as Louth explains, this difference was a later creation of the 3rd and 4th centuries. Discomfort with similarities between Christianity and Platonism led certain Fathers to assert a new concept: creation ex nihilo. “The doctrine was unknown to pagan philosophy,” explains Louth, “and emerged only slowly and uncertainly in early Christian theology.” In the rise of the Arian controversy, explains Louth, both the Orthodox and the Arians agreed on creation ex nihilo. “Arius consigned the Word to the created order; the Orthodox consigned him to the realm of the (now strictly divine). Nicaea can then be seen, as Friedo Ricken has put it, as a ‘crisis for early Christian Platonism.'” “The soul’s kinship with the divine was destroyed by the doctrine of creation ex nihilo,” because the soul was now a “creature” of the divine, a created thing and not coeternal. “Neither for Plato nor for Origen were souls created: they were pre-existent and immortal.” 
Says E. R. Dodds, “After three centuries of controversy virtually all of Origen’s innovations were condemned as heretical by an edict of Justinian in 543. It was not Origen but Augustine who determined the future pattern of Western Christianity.”  Augustine was a complex figure with a complex theology and Terryl Given’s When Souls Had Wings does a very good job of explaining these shifts. 
Not long after the assertion of creation ex nihilo and the conversion of Constantine, Christians became increasingly heavy handed. Constantine himself actually promoted toleration; it was Theodosius who outlawed pagan worship as a way to demonstrate his piety to the bishops in 380. From this point on, Christians became increasingly harsh attacking pagans and destroying their shrines. Justinian shut down the Platonic academy in 529.
It was in this environment that Proclus, who never converted to Christianity, took over the Academy in Athens around 430, the one Justinian would later shut down. Reading Brent James Schmidt’s dissertation on utopianism in antiquity shows the stark contrast between the earliest Egyptian Christian monks and Proclus’s academy. Both strove for piety but the Christians were overly harsh, and promoted extreme asceticism imposed through corporal punishment. Proclus’s academy was different. “Through the principles of love and unity,” explains Schmidt, “Proclus often brought out the best in the members of his community. Thus, Proclus was able to set the proper pious, religious example for his neo-Platonic utopia.” And later, “Proclus led his community through philanthropy instead of compulsion.”  Which sounds more like Jesus?
Living in this new intolerant Christian world, Proclus only wrote one tract against the Christians, On The Eternity of the World, a treatise rejecting creation ex nihilo. Most of Proclus’s writings focussed on extending Plato’s philosophy in which preexistance and divinization were central. Said E. R. Dodds, Proclus
expounded and harmonized all earlier theologies ‘both Greek and barbarian’, and critically sifted the theories of all pervious commentators, keeping what was fruitful and rejecting the rest. Proclus, then, is not a creative thinker even in the degree of Iamblichus, but a systematizer who carried to its utmost limits the ideal of the one comprehensible philosophy that should embrace all the garnered wisdom of the ancient world. 
Indeed, Proclus became a principle channel through which deification and preexistance survived in the West and this was done largely through misattributed texts that I described in these posts. I find this rather remarkable. Most Christian leaders did not like the idea of accepting pagan authors, and Proclus would have seemed particularly bad because he stubbornly refused to join the Christians in a time when most of the empire had converted. The fact that he refused to accept Christianity over creation ex nihilo (among other things) is also remarkable. So that fact that Proclus’s ideas survived in a Christianized form under the name of Dionysius and then in a Muslim form under the name of Aristotle in the Book of Causes is also remarkable. Christians so influenced by Proclus often promoted preexistance and deification. Such ideas could get one in trouble, but Proclus’s difficult, mystical style seemed to allow adherents to dodge and weave a bit on exactly what they were asserting. 
Ben Park’s recent article in Dialogue on the emergence of Mormon materialism paints a very interesting picture of how the rejection of creation ex nihilo emerged along side preexistance and deificaiton in early Mormonism.  Again we see these central Mormon tenets linked together. Again, Proclus appears to be an important conduit for preserving these ideas that many forms of Christian orthodoxy sought to crush for thousands of years. The fact that Joseph Smith put things back together the way he did is, again, remarkable. According to Catherine Albanese, Joseph Smith “picked up the scattered pieces of light in his world in order to repair and reconstruct a Hermetic whole.”  With the caveat that much of what was called Hermetic in fact derived from Proclus (as I mention in the previous posts) I’d simply say Amen. To me this all looks divine.
 Quoted in Karen L. King. What is Gnosticism? (Cambridge: The Belkap Press of Harvard University Press, 2003), 59-60, 65. King notes that von Harnack drew upon certain Fathers, particularly Tertullian for this view. King summarizes Tertullians views as “insisting that there are limits to Jesus’ injunction to seek and find. Once one has found, he says, it is time to quit seeking.” 29.
 E. R. Dodds, Pagan and Christian in an Age of Anxiety: Some Aspects of Religious Experience from Marcus Aurelius to Constantine. (Cambridge: University of Cambridge Press, 1965), 74.
 Andrew Louth, The Origins of the Christian Mystical Tradition: From Plato to Denys (Oxford: Clarendon, 1981), xiii.
 Louth, Origins of the Christian Mystical Tradition, 75-76.
 Dodds, Pagan and Christian, 131-32
 I moved recently and my stuff (including Givens’s book) is in transit, so I can’t cite particular pages.
 Brent James Schmidt, Utopian Communities of the Ancient World: Idealistic Experiments of Pythagoras, the Essenes, Pachomius, and Proclus (Lewiston, NY: Edwin Mellen, 2010), 180, 185. Schmidt is LDS and did his dissertation at the University of Colorado. Jack Welch wrote the introduction to the book.
 Proclus, The Elements of Theology, A Revised Text with Translation, Introduction and Commentary by E. R. Dodds, 2d ed. (Oxford: Clarendon, 1963), xxv.
 A good example of this is Meister Eckhart, who drew very consciously on Proclus and is quite mystical. Eckhart was called up on charges and actually intended to bring Proclus’s writings as part of his defense (I heard this at a paper given on Eckhart; the presenter pointed out that Proclus was likely not the best defense). Eckhart died before he made it to trial but was condemned after (he nonetheless had a huge impact on later mystical and pietist movements as I mention in previous posts). There has since been a big effort among Eckhart’s devotee’s to get him back in good standing with the Vatican, arguing that he was perfectly orthodox, and the presenter was one such person. The commentator said to the presenter “what about this line from Eckhart: ‘Love was in the Bride chamber before God was God.’ ‘Before God was God!’ That’s like that the question people sometimes ask ‘What was God doing before he created us.’ That’s like the question on steroids!” I thought “wow, sounds Mormon,” but I didn’t say anything because pointing out the similarities to Mormonism clearly wasn’t in line with the presenters agenda of showing Eckhart as orthodox.
 Benjamin Park, “Salvation through a Tabernacle: Joseph Smith, Parley P. Pratt, and Early Mormon Theologies of Embodiment,” Dialogue 43, no. 2 (2010).
 Catherine Albanese, A Republic of Mind an Spirit: A Cultural History of American Metaphysical Religion (New Haven: Yale University Press, 139.