When I was in Sunday school, when I was eleven or twelve and would win one piece of candy for showing up and another for memorizing the weekly Bible verse, we learned about the Ten Commandments.
1 Then God spoke all these words:
2 I am the Lord your God, who brought you out of the land of Egypt, out of the house of slavery; 3 you shall have no other gods before me. 4 You shall not make for yourself an idol, whether in the form of anything that is in heaven above, or that is on the earth beneath, or that is in the water under the earth. 5 You shall not bow down to them or worship them; for I the Lord your God am a jealous God, punishing children for the iniquity of parents, to the third and the fourth generation of those who reject me, 6 but showing steadfast love to the thousandth generation of those who love me and keep my commandments. 7 You shall not make wrongful use of the name of the Lord your God, for the Lord will not acquit anyone who misuses his name.
We learned that the first commandment, the 'no other gods before me' bit, said that God comes first. The second commandment means that we shouldn't worship idols, like Chemosh the Fish-Headed God of the Moabites or nice cars or Yojo or career success or Dionysius. The third commandment obviously meant we shouldn't say, 'Oh my God,' but we went ahead and agreed that damn and the F-word were probably out, too.*
Chemosh isn't an idol, he's a false god.
The 'before' in the first commandment isn't a word indicating sequence, it indicates presence. That is, God tells the Israelites not merely that he must be their first and best, but that he must be their only, all other gods are false. Oh, sure, they might be real, but they're empty.
The second commandment can't be a condemnation of worshipping other gods, because this is covered under the first commandment. The second commandment condemns idolatry, a worship practice.
An idol isn't a god, it's an image.
No one ever thought their little statue of Chemosh or Zeus or Yojo or the Woman of Willendorf was god, they thought these statues were portals or points of connection to spiritual forces, perhaps personified as gods.
We're not quite sure, honestly, but it seems as if the Woman of Willendorf and similar statues, with large thighs and pendulous breasts, would grant a user similar fertility. This is called sympathetic magic, the belief that things are connected to their images. Similarly, it has been suggested that the cave paintings in France, images of successful hunts, were believed to actually cause successful hunts.
Certainly, people would drink the blood of bulls hoping to become strong. (It is this practice that the Biblical prohibitions on consuming blood were written to address.) Today, in places, people consume rhino horns and tiger penises and asparagus as aphrodisiacs.
(If you're like me and were puzzled as to why it was tough to find asparagus on Valentine's Day, now you know that sympathetic magic is the reason.)
In Bible times, worshippers of Ba'al Hadad would make sacrifices in front of bull statues. No one ever thought that Ba'al Hadad was actually a bull; he obviously looks like a human being. However, everyone knew that Ba'al Hadad was powerful, and so are bulls, so by sacrificing to a bull statue, one might hope to manipulate Ba'al Hadad to access his power for one's own purposes.
A king (seen, in some cultures, as a god) would make statues 'in his own image' to mark the boundary of his kingdom. No one thought that a statue of the king was the king himself, but this symbol of the king's presence was respected throughout the kingdom.
The God of the Jews was presenting himself as transcendent, having no body, eschewing physical manifestation. Well, not quite. God doesn't seem to have a problem with appearing as a torch and firepot or a mysterious stranger or a luchador or a burning bush or a pillar of cloud or a pillar or fire. However, each time that God appears, he does so entirely on his own terms.
The second commandment condemns misrepresenting and manipulating God.
Names are a sort of image. A god's name would be used in curses and hexes to invoke that god. The third commandment says that God's name ought not be used frivolously, and that when it is used, it ought to be taken seriously; a vow made in God's name ought to be kept. We ought not use God's name to boss him around, to make him operate on our terms.
Now, while Moses was up on the mountain learning all of these things about God being transcendent, the only one worthy of worship, who ought not be misrepresented, manipulated, or wrongfully invoked, the Israelites were downstairs, misrepresenting and attempting to manipulate and wrongfully invoke God. That is, while they sure were glad that God delivered them from Egypt, life in the desert was unpleasant, and they wanted him to get the lead out; he was taking too long up on that mountain with Moses. They made a calf out of the gold they had lying around. They didn't think that a literal calf had rescued them from Egypt, but they identified the calf statue with the divine power behind that deliverance. They didn't quit God and try to go shopping for a new god, they wanted to control their patron deity.
At its best, the church builds grand cathedrals with tall steeples, reminding us that God doesn't live in the building but over it. The church must remind us that God can not be apprehended.
People gather around positive statements, though. I like God, but I'd like him better if I could see him, and I'd like him best if I could make him in my own image. Books about what God is like and how to get what you want from him sell better than books about how you don't know as much about God as you'd like but you ought to trust him through uncertainty, rather than trying to push him around like he's your butler.
Martin Luther rightly stated that no one can break any of God's laws without first breaking the first commandment. People misrepresent God when they would rather be worshipping another god, they manipulate God when they want him to give them something more important to them than God himself, when this other end becomes their real god, and they misuse God's name when they think they know better than God how he ought to do his job.
*This misunderstanding of the Ten Commandments might well simply be my own, I mean no disrespect to my Sunday school teacher. In fact, Miss Letty was actually a very good Sunday School teacher; she didn't just teach us Bible stories, she taught us the Bible, and how it tells one story over and over, from beginning to end. Every Sunday morning, we would pray for missionaries all over the world. If she did slightly misinterpret the first three commandments, she wasn't doing much worse than the authors of the Westminster Catechism***.
**There are a couple of tangled-up things here. What I'm calling the first and second commandments are actually intertwined, textually. Verse 3 is clearly about the first commandment, and verse 4 is clearly about the second, but verses 5 and 6 most clearly apply to what I'm reading as the first commandment. I think this entanglement is due to a second issue of entanglement. That is, not many people in the Old Testament Jewish culture would have worshipped God with idols, nor would they have worshipped other gods but eschewed idols: in general, the first two commandments were violated simultaneously. The exceptions that come to mind are the golden calf (Exodus 32) and Nehushtan, the bronze serpent (II Kings 18:1-4), where symbols were used wrongly to worship God, rather than to other gods.
***For Presbyterian and Anglican Nerds:
The Westminster Catechism exegetes the first and third commandments quite well, but horribly botches the explanation of the second (Q109 in the Larger, Q51 in the Shorter), using it to justify the regulative principle of worship, that is, that God should only be worshipped by the means he himself proscribed. The second commandment doesn't quite say that; it condemns a specific practice. In its condemnation of something that God himself does not, the Westminster Catechism misrepresents God's will, and, on this point, is, ironically, idolatrous.