If you're trying to set up some rules for a bunch of nomads wandering through the desert — rules that will keep them out of trouble, not to mention alive — "thou shalt not kill each other" might seem like a logical place to start.

But the Ten Commandments don't begin with a prohibition against murder. They begin with a commandment to put God first.

It's both the most obvious and the most baffling commandment, depending on whether you're a believer or not. On the one hand, God comes across a bit arrogant, mentioning his needs first, wanting to be the top dog. On the other hand, following God is seen as the foundation for all the other commandments that follow.

There is disagreement among various faiths about which part of the Decalogue constitutes the First Commandment. Jews count it as verse 2 of Exodus 20: "I am the Lord thy God, which have brought thee out of the land of Egypt, out of the house of bondage." Other religions see that more as the back story. Catholics and some Lutherans choose verses 3 through 6 as the First Commandment, including the prohibition against graven images.

For most Protestants and Eastern Orthodox, the First Commandment is "Thou shalt have no other gods before me." It is this version of the Ten Commandments that appears most often in displays, and it is the version that we have chosen for the series that began last week and runs until June 16.

"Thou shalt have no other gods before me" was a radical notion in the polytheistic Middle East of 3,500 years ago, where it was common to have national gods and local gods and household gods, fertility gods and gods for the crops and gods to protect people from harm. But the "I Am" of Exodus 3:14 asked to be the one and only.

Monotheism was revolutionary and maybe, argues Leonard Shlain in the book "The Alphabet Versus the Goddess," also dangerous. People who believed in many gods, he argues, respected the gods of other people and expected their gods to be respected in return. But to believe that only one God exists, an abstract God that different people might perceive in different ways, "loosed into the world an odious impulse," he argues. The question of whose perception of the one deity is the correct one "has goaded monotheists to wage war with an intensity and purpose never witnessed in polytheistic cultures."

On the other hand, this God with a capital G set down strict rules for his people.

By the time the Ten Commandments were brought down Mount Sinai by Moses, the Jews already had some history with this God, whom they believed had created everything, had made covenants with Abraham and Noah, and had delivered them from slavery. By this reckoning, then, God was reality. And three millennia later, to choose something or somebody else instead of this God to guide you would be choosing something that is an illusion, says Tom McClenahan, academic dean of the Salt Lake Theological Seminary.