What are the Ten Commandments?
I was reviewing the Ten Commandments and came across this entry from Wikipedia. What it says, to my surprise, is that the precise definition of Ten Commandments depends on which denomination you belong to. The passages of reference, Exodus 20:2-17 and Deuteronomy 5:6-21, actually contain 14-15 imperative statements, yet the Bible itself talks about commandments been 10, as in Exodus 34:28. So it is no surprise that denominations have chosen to slice the original statements differently.
By far the most difference lies in whether Exodus 20:3-4 is treated as one commandment (Jewish, Catholic, Lutheran) or two (Protestant, Anglican, Orthodox). Treating them as one basically extends the meaning of idolatry from just making an image of an idol and worshiping it (verse 4) to much more general idea of having other gods before the God of Jews (verse 3). On the other hand, if the commands are separated , idolatry can be interpreted in much more narrow sense.
Regardless of which partition you accept, I think it is quite clear that making and worshiping a physical idol also violates the command of not having other gods before God. Hence, extending the meaning of the term “idolatry” to “having other gods before God” is reasonable.
This decision has many other implications. Martin Luther has long ago noticed that commandments 2-10 are all subordinate of the first commandment. In other words, you cannot break commandment X (where X=2-10) unless you have already broken commandment 1. You do not commit adultery unless something in your life (e.g. physical pleasure) has become more important to you than God. You do not bear false witness unless something in your life (e.g. status, reputation, money) has become more important to you than God. Basically, almost everything wrong that we can do ultimately stems from treating something else more important than God and hence is idolatry.