Gnosticism is a divers system of spiritual beliefs that incorporated pagan, Greek, and Christian ideals to formulate its own system. Each Gnostic teacher added or changed the Gnostic beliefs to fit their own individualized ideals. The first mentions of some of these Gnostic ideals were developed from the 2nd to 4th century AD. The Church exposed these ideals as unorthodox and unchristian but sadly, even today, we can still see some of the ideals being taught. There are a few primary teachers that developed ideals that are familiar still today: Marcion of Sinope, Valentinus, Theodotus of Byzantium, Arius of Alexandar, Pelagiu, Cerinthus, Menander, Sabellius, Basilides, and Montanus. There are other early Gnostic teachers but their forms of Gnosticism are far more separated from orthodoxy Christianity. These same teachings influence modern religions and movements such as the Word of Faith movement, Jehovah's Witnesses, Mormonism, and Islam.
The Gnostic Doctrine of God
God of the Old Testament is different from the God of the New Testament (Marcion of Sinope 120AD)
God did not create the universe, but a lesser being created it (Cerinthus 120AD; Valentinus 140AD; Basilides 125AD; Arius of Alexandar 320AD)
Dualism/Manichaeism
Arianism
Jehovah's Witnesses
The world was created by angels (Menander 2nd Century; Cerinthus 120AD)
Menanderism
Jehovah's Witnesses
Denies God The Father as creator
God is one being that reveals himself chronologically in three modes through history (Sabellius 210AD; Paul of Samosata 250AD)
Modalism/Monarchianism (Sabellianism)
Oneness Pentecostalism
Denies The Triune God
God is not sovereign and is limited by Man's free will (Pelagius 5th century AD)
Semi-Pelagianism
Word of Faith movement
Arianism
Denies God's sovereignty and omniscience.
The Gnostic Doctrine of Jesus
Jesus was not actually physical but only appeared to be (Marcion of Sinope 120AD; Valentinus 140AD)
Docetism
Islam (the crucifixion)
Jesus did not actually physically die on the cross and thus did not physical resurrect from the dead.
Jesus did not actually have a physical body, thus was not the incarnate God.
Denies Jesus' physical death and resurrection.
Jesus was just a created human until baptism where he was then granted supernatural powers and then adopted by God (Cerinthus 120AD; Theodotus of Byzantium 190AD; Paul of Samosata 250AD; Arius of Alexandar 320AD)
Jesus is not the eternal Son of God
Jesus is not God incarnate
Adoptionism
Word of Faith movement
Arianism
Jehovah's Witnesses
Subordinationism
Islam
Christ left Jesus at the crusifixtion (Cerinthus 120AD)
Word of Faith movement
Denies Jesus' eternal existence
Denies Jesus' divinity as God the Son.
Denies the Triune God
The Gnostic Doctrine of The Bible
Only selected portions of the Bible are true (Marcion of Sinope 120AD; Cerinthus 120AD)
Jehovah's Witnesses
Islam
True knowledge of God only comes through secret revelations (Valentinus 140AD; Basilides 125AD)
Word of Faith movement
Extra biblical prophetic revelations (Basilides 125AD; Montanus 177AD)
Montanism
Word of Faith movement
Divine revelations from Angels (Cerinthus 120AD)
Word of Faith movement
Islam
Mormonism
The Church exposing Gnosticism
As exposed above, these modern teachings are not new. Despite the modern continuation of Gnostic teachings, the church addressed and exposed these teachings as heresy a long time ago. You can read the early writings of the church teachers bellow at: https://www.ccel.org/fathers.html.
The last words of Paul in his First Epistle to Timothy are usually taken as referring to Gnosticism, which is described as "Profane novelties of words and oppositions of knowledge falsely so called [antitheseis tes pseudonomou gnoseos — the antitheses of so-called Gnosis] which some professing have erred concerning the faith". Most probably Paul's use of the terms pleroma, the æon of this world, the archon of the power of the air, in Ephesians and Colossians, was suggested by the abuse of these terms by the Gnostics. Other allusions to Gnosticism in the New Testament are possible, such as Titus 3:9; 1 Timothy 4:3; 1 John 4:1-3.
The first anti-Gnostic writer was Justin Martyr (d. c. 165). His "Syntagma" (Syntagma kata pason ton gegenemenon aireseon), substantially contained in the "Libellus adv. omn. haeres.", usually attached to Tertullian's "De Praescriptione"; Justin's anti-Gnostic treatise on the Resurrection (Peri anastaseos) considerable fragments are extant in Methodius' "Dialogue on the Resurrection" and in John Damascene's "Sacra Parellela". Justin's "Comendium against Marcion", quoted by Irenæus (IV.6.2 and V.26.2), is possibly identical with his Syntagma". Immediately after Justin, Miltiades, a Christian philosopher of Asia Minor, is mentioned by Tertullian and Hippolytus (Against the Valentinians 5, and Eusebius, Church History V.28) as having combated the Gnostics and especially the Valentinians.
Theophilus of Antioch (d. c. 185) wrote against the heresy of Hermogenes, and also an excellent treatise against Marcion (kata Markionos Logos). The book against Marcion is probably extant in the "Dialogus de rectâ in Deum fide" of Pseudo-Origen. For Agrippa Castor see BASILIDES.
Hegesippus, a Palestinian, traveled by way of Corinth to Rome, where he arrived under Anicetus (155-166), to ascertain the sound and orthodox faith from Apostolic tradition. In consequence he wrote five books of Memoirs (Upomnemata) "in a most simple style, giving the tradition of Apostolic doctrine", becoming "a champion of the truth against the godless heresies" (Eusebius, Church History IV.7 sqq. and IV.21 sqq.). Rhodon, a disciple of Tatian, Philip, Bishop of Gortyna in Crete, and a certain Modestus wrote against Marcion
The greatest anti-Gnostic controversialist of the early Christian Church is Tertullian (b. 169), who practically devoted his life to combating this dreadful sum of all heresies. We need but mention the titles of his anti-Gnostic works: "De Praescriptione haereticorum"; "Adversus Marcionem"; a book "Adversus Valentinianos"; "Scorpiace"; "De Carne Christi"; "De Resurrectione Carnis"; and finally "Adversus Praxeam".
Irenaeus (Against Heresies I.15.6) and Epiphanius (xxxiv, 11) quote a short poem against the Oriental Valentinians and the conjuror Marcus by "an aged" but unknown author; and Zachaeus, Bishop of Caesarea, is said to have written against the Valentinians and especially Ptolemy. Beyond all comparison most important is the great anti-Gnostic work of Irenæus, Elegchos kai anatrope tes psudonymou gnoseos, usually called "Adversus Haereses". It consists of five books, evidently not written at one time; the first three books about A.D. 180; the last two about a dozen years later. Irenæus knew the Gnostics from personal intercourse and from their own writings and gives minute descriptions of their systems, especially of the Valentinians and Barbelo-Gnostics. A good test of how Irenæus employed his Gnostic sources can be made by comparing the newly found "Evangelium Mariae" with Against Heresies I.24. Besides his great work, Irenaeus wrote an open letter to the Roman priest Florinus, who thought of joining the Valentinians; and when the unfortunate priest had apostatized, and had become a Gnostic, Irenaeus wrote on his account a treatise "On the Ogdoad", and also a letter to Pope Victor, begging him to use his authority against him.
Eusebius (Church History IV.23.4) mentions a letter of Dionysius of Corinth (c. 170) to the Nicomedians, in which he attacks the heresy of Marcion.
Clement of Alexandria (d. c. 215) only indirectly combated Gnosticism by defending the true Christian Gnosis, especially in The Pedagogue I, Stromata II, III, V, and in the so-called eighth book or "Excerpta ex Theodoto".
Origen devoted no work exclusively to the refutation of Gnosticism but his four books "On First Principles" (Peri archon), written about the year 230, and preserved to us only in some Greek fragments and a free Latin translation by Rufinus, is practically a refutation of Gnostic dualism, Docetism, and Emanationism.
Amongst anti-Gnostic writers we must finally mention the neo-Platonist Plotinus (d. A.D. 270), who wrote a treatise "Against the Gnostics".
About the year 300 an unknown Syrian author, often called by the literary pseudonym Adamantius, or "The Man of Steel", wrote a long dialogue of which the title is lost, but which is usually designated by the words, "De rectâ in Deum fide". This dialogue, usually divided into five books, contains discussions with representatives of two sects of Marcionism, of Valentinianism, and of Bardesanism. The writer plagiarizes extensively from Theophilus of Antioch and Methodius of Olympus, especially the latter's anti-Gnostic dialogue "On Free Will" (Peri tou autexousiou).
First Council of Nicaea 325AD (May 20-June 19) addressed Arianism, the nature of Christ, and validity of baptism by heretics.
First Council of Constantinople 381AD (May-July) addressed Arianism, Apollinarism, Sabellianism, and the Holy Spirit.
Philastrius of Brescia, a few years later (383), gave to the Latin Church what Epiphanius had given to the Greek. He counted and described no fewer than one hundred and twenty-eight heresies, but took the word in a somewhat wide and vague sense. Though dependent on the "Syntagma" of Hippolytus, his account is entirely independent of that of Epiphanius. Another Latin writer, who probably lived in the middle of the fifth century in Southern Gaul, and who is probably identical with Arnobius the Younger, left a work, commonly called "Praedestinatus", consisting of three books, in the first of which he describes ninety heresies from Simon Magus to the Praedestinationists.
Council of Ephesus 431 (June 22-July 31) addressed Theotokos, and Pelagianism.
Council of Chalcedon (451) Theodoret wrote a "Compendium of Heretical Fables" which is of considerable value for the history of Gnosticism, because it gives in a very concise and objective way the history of the heresies since the time of Simon Magus.
Council of Orange (529AD) made numerous proclamations against what later would come to be known as semi-Pelagian doctrine.
Third Council of Constantinople 680-681AD (November 7-September 16) addressed Monothelitism, the human and divine wills of Jesu
The Belgic Confession (1567AD) addressed the Arminian Controversy
The Chicago Statement of Biblical Inerrancy (1978AD) addressed montanism and the Word of Faith movement.
Despite the centuries of exposing Gnostic ideals as heresy and unorthodox Christianity, modern charismatic evangelical Christian teachers fail to learn what has been exposed and addressed throughout church history. Instead, through ignorance or willful selfishness, they continue to perpetuate heresy under the false claim of Christianity that corrupts essential truths that impact the salvation of their followers.