To begin, right away I want to state that I believe that the Second Council of Nicaea (787 AD) was the most violent, egregious attack on Galatians 1:6-9 in the history of the Church. That is to say, it was a flagrant, pernicious assault on the Gospel. Every Christian - Protestant or not - should know about this council, and hopefully this article furthers that.
The Second Council of Nicaea is regarded by Catholics and Eastern Orthodox Christians as the 7th ecumenical council, meaning that they affirm it to be infallible in matters of doctrine. It was a response to the Iconoclast controversy, which surrounded the permissibility of creating and venerating religious images.
It overturned the earlier Council of Hieria (754 AD), which had also declared itself the 7th ecumenical council, and forbade the use of icons and images in worship:
Council of Hieria (754 AD)
Supported by the Holy Scriptures and the Fathers, we declare unanimously, in the name of the Holy Trinity, that there shall be rejected and removed and cursed out of the Christian Church every likeness which is made out of any material and colour whatever by the evil art of painters.
Whoever in future dares to make such a thing, or to venerate it, or set it up in a church, or in a private house, or possesses it in secret, shall, if bishop, presbyter, or deacon, be deposed; if monk or layman, be anathematised, and become liable to be tried by the secular laws as an adversary of God and an enemy of the doctrines handed down by the Fathers.
8 If anyone ventures to represent the divine image (χαρακτήρ) of the Word after the Incarnation with material colours, let him be anathema!
9 If anyone ventures to represent in human figures, by means of material colours, by reason of the incarnation, the substance or person (ousia or hypostasis) of the Word, which cannot be depicted, and does not rather confess that even after the Incarnation he [i.e., the Word] cannot be depicted, let him be anathema!
The above council was summoned by the Iconoclast Byzantine emperor Constantine V (718-775 AD). However, this council would only stand for a few decades, as after Constantine V died, the empress Irene of Athens (750-806 AD), who was sympathetic to icons, convoked the Second Council of Nicaea. This same empress Irene would later gouge out the eyes of her own son, Constantine VI, and then imprison him until he died, in order to become sole ruler of the Byzantine empire.
This council made image veneration into a sine qua non of Salvation. It did not merely decree that image veneration was permissible, but rather was an essential part of orthodoxy, without which someone was to be cut off from the Body of Christ:
Second Council of Nicaea (787 AD)
If anyone does not salute such representations as standing for the Lord and his saints, let him be anathema.
Let them who do not venerate the holy and venerable images be anathema!
To those who have a doubtful mind and do not confess with their whole hearts that they venerate the sacred images, anathema!
We salute the venerable images. We place under anathema those who do not do this.
[We have likewise decreed] that these images are to be reverenced (προσκυνεῖν), that is, salutations are to be offered to them. The reason for using the word is, that it has a two-fold signification. For κυνεῖν in the old Greek tongue signifies both "to salute" and "to kiss". And the preposition προς gives to it the additional idea of strong desire towards the subject; as for example, we have φέρω and προσφέρω, κυρῶ and προσκυρῶ, and so also we have κυνέω and προσκυνέω. Which last word implies salutation and strong love; for that which one loves he also reverences (προσκυνεῖ) and what he reverences that he greatly loves, as the everyday custom, which we observe towards those we love, bears witness, and in which both ideas are practically illustrated when two friends meet together.
If anyone does not accept this our Holy and Ecumenical Seventh Synod, let him be anathema from the Father and the Son and the Holy Ghost, and from the seven holy Ecumenical Synods!
Now anathema is nothing less than complete separation from God. For if any are quarrelsome and will not obediently accept what has now been decreed, they but kick against the pricks, and injure their own souls in their fighting against Christ.
Notice the following from the above:
Any person who has even the slightest respect for the purity and content of the Gospel of grace is appalled at what they've just read. This council has turned the Gospel into veneration of pieces of wood and stone, which have been painted to look like Biblical figures.
Often, the discussion around images will get bogged down in the distinction, or lack thereof, between worship and veneration. Such a discussion is just a distraction. The real issue is that they have made the veneration of images a requirement for Salvation, which is a flagrant, blasphemous assault on the pure Gospel, of the worst sort.
The Gospel message is clearly elucidated in Scripture (1 Corinthians 15:1-8), it is defined as God's message of Salvation (Romans 1:16: 1 Corinthians 1:17-18, Ephesians 1:12-14: 2 Timothy 1:10), it is carefully and bitterly guarded against any attempt to add anything at all to it (Acts 15:5-11: 2 Corinthians 11:3-4, Galatians 1:6-9, 2:11-14), and it does not include venerating icons. The Second Council of Nicaea violently overthrew the Bible's testimony of the Gospel, and replaced it with another Gospel, which included something expressly forbidden in both Testaments.
While the main goal of this article is to point out how the Gospel has been fundamentally corrupted by Nicaea II, the following demonstrate that the practice of venerating icons is neither Biblical, nor a practice of the early Church:
Jesus did not die on the cross, and bear our sins, and rise from the dead, so that we would have to venerate icons to be saved. This council, accepted by most of the Churches claiming Apostolic succession, is an irreparable corruption of the Gospel.
Any Christian who wishes to please the Lord Jesus Christ, and protect the integrity of the Gospel, must reject the Second Council of Nicaea, and all of its unbiblical accretions.