The second commandment forbids making a carved image or any likeness of anything in heaven or earth, and bowing to it. Christians have read that in strikingly different ways, and the difference is visible the moment you walk into a building: an church covered in icons, a church with statues, a Reformed meeting house with bare walls and a pulpit in the middle.
One detail explains some of the confusion. The traditions do not number the commandments the same way. Catholic and Lutheran numbering folds the prohibition of images into the first commandment about having no other gods, and gets to ten by splitting coveting into two. Reformed, Orthodox, and most other Protestant numbering makes images a separate second commandment. Nobody is deleting anything, and the accusation that Catholics removed a commandment is false. But the numbering does affect emphasis, since a clause inside another commandment reads as an application of it, while a standalone commandment reads as its own rule.
The deeper question is what changed, if anything, when God became visible. That is where the actual argument is.
Exodus 20:4-6
4"You shall not make for yourselves an idol, nor any image of anything that is in the heavens above, or that is in the earth beneath, or that is in the water under the earth: 5you shall not bow yourself down to them, nor serve them, for I, the LORD your God, am a jealous God, visiting the iniquity of the fathers on the children, on the third and on the fourth generation of those who hate me, 6and showing loving kindness to thousands of those who love me and keep my commandments.
Every tradition agrees that worship belongs to God alone, that idolatry is a grave sin, and that no image can represent the divine nature, which is invisible and uncircumscribable. Every tradition also agrees that God commanded certain images in the and temple: cherubim over the ark, in the curtains, and carved on the walls, plus the bronze serpent. So no one holds that the commandment forbids all representational art. What is disputed is whether images of Christ and the saints may be made, and what may be done in front of them.
Icons are required by the incarnation
Because God took a body that could be seen and touched, he can be depicted. Refusing to depict Christ denies that the incarnation was real.
What it claims
The Old Testament prohibition was given to a people who had seen no form on the day God spoke at Horeb, and it forbids depicting what has no shape. That situation changed. The invisible God became visible, and what is visible can be painted. John of Damascus put it directly: he did not venerate matter but the God who became matter for his sake. The council was careful about vocabulary, distinguishing veneration, which may be given to an image and passes to the person it depicts, from worship, which belongs to God alone. On this account iconoclasm is not extra caution but a christological error, since it implies Christ's humanity was not fully depictable and therefore not fully real.
Who holds it
Eastern Orthodoxy and the Oriental Orthodox churches. Defined at the Second Council of Nicaea in 787, the seventh ecumenical council, and celebrated annually as the Triumph of Orthodoxy. Defended by John of Damascus and Theodore the Studite during the iconoclast controversy.
The texts it stands on
Colossians 1:15 Christ is the image of the invisible God. The word is eikon, and the argument turns on it.
John 1:14 The Word became flesh and dwelt among us, and we have seen his glory. Seeing is the claim.
Exodus 25:18-20 God commands cherubim of hammered gold on the mercy seat, in the holiest place, which sets a limit on how absolute the prohibition can be.
Strongest case
It is the position of an ecumenical council that Catholics and Orthodox both receive, and its argument is genuinely christological rather than merely aesthetic. It also has the strongest account of why the Old Testament situation changed, which is the question the other views must also answer.
Hardest question
The distinction between veneration and worship is clearer in Greek than in practice, and critics ask whether ordinary people making the distinction reliably is a realistic expectation. Protestant critics also note that Deuteronomy 4 grounds the prohibition precisely in Israel seeing no form, and argue that the gives us Christ's humanity to depict but not his divinity, so an image of Christ inevitably represents less than he is.
Holding the map
This is a case where the practical stakes are lower than the historical bitterness suggests. The iconoclast controversy was violent, the Reformation stripping of altars destroyed a great deal, and both sides accused the other of the gravest sin available. Today most Christians visit each other's buildings without incident.
It is still worth thinking through, because the underlying question does not go away: whether God has told us how he wants to be approached, or left that to Christian freedom. Everything from music to to church architecture is downstream of the same question, and the traditions are consistent. Those who say worship must be positively commanded are consistent about images, songs, and instruments alike. Those who say what is not forbidden is permitted are consistent in the other direction. Knowing which principle you hold explains more of your own tradition than any single argument about pictures.
Questions that press on this one
None of these stands on its own. What you conclude here narrows what you can say there.
