Judaism, Christianity, and Islam are referred to as Abrahamic religions, a description aiming to head off the clash of civilizations by emphasizing a common connection to the patriarch whose name means ''father of multitudes."

Yet Jews, Christians, and Muslims are more than mere cousins. The imaginative breakthrough represented in the story of Abraham offers a first measure of the meaning of human existence. If his descendants were more fully in touch with that meaning, Iraq would be a different place today, and the religions would not be on the cusp of war.

Abraham's story comes to us from Genesis. What makes it important is all that precedes it. The Bible begins as a set of creation myths, narratives about Adam, Eve, Cain, Abel, Noah, the Flood, the tower of Babel -- anecdotes that few contemporary readers take in any literal sense. They are stories from the era of ''once upon a time," and they define the concern of the Creator as extending to the entire scope of creation.

But at the end of the 11th chapter of Genesis, something new happens, a shift from the universal to the specific, from timelessness to ''that time then"; from never-never land to a particular locale -- a bridge of land between the Tigris and Euphrates rivers. One day on our calendar, a specific individual, whom scholars believe actually to have existed, became the subject of the biblical text. That was the true beginning of the world-view we take for granted.

''Leave your country, your family, and your father's house for the land I will show you," God said to this person. ''I will make you a great nation. I will bless you and make your name famous, so it will be used as a blessing."

The call of Abraham marks the beginning of human historical consciousness, a direct consequence of the revolutionary affirmation that God meets human beings by meeting one human being at one time, and at one place. The God who addresses Abraham in effect orders him to leave the realm of the purely mythical for ''the land I will show you."

Here is the difference between Abraham's God and the gods of Ur or Egypt: This God acts not out of time, but in it; not in the other world, but in this one; not in heaven, but on earth. This Creator is invested in creation not in general, but in particular. Therefore history -- what happens here and now -- is of ultimate significance. This means that the value of mere abstractions must be measured against the real-world consequences of their implementation.

The war in Iraq today was launched without regard for such consequences, and we see the result. The genius insight of Genesis is that when God is understood as the God of history, then history -- what happens in time among human beings -- takes on absolute value. The ideal, therefore, must always be measured against the real.

The death of each man, woman, and child who has died in Iraq across the last three years equals, in the eyes of the God who called Abraham by name, the death of all that exists. Each person is of infinite worth. If war makers had calculated their decisions on this scale, they would have found another way to proceed. War must be a last resort, not a first reaction.

But the story of Abraham makes another point. In addition to being the God of history, this God is the God of freedom. Not freedom in the shallow rhetoric of American politics, but freedom that defines each human choice as having as much significance as the very acts of God.

Abraham's call, with the fate of multitudes at stake, meant nothing until Abraham said yes to it. But the possibility of that yes presumed the possibility of its opposite. God, in freedom, initiates. Abraham, in freedom, responds. But as subsequent verses of Genesis make clear, Abraham's will and God's are not identical, and that is the way this God wants things to be.

A God of freedom invites a response, but does not coerce it. Why? Because in this way the God of history makes humans responsible for history.

Jews, Christians, and Muslims bear the weight of this precious legacy, embodied in our common ancestor. History matters absolutely. So does each human life. And so does every human choice. Absolute responsibility follows. That this wisdom first showed itself in the landscape across which war now rages is another reason to end it.

James Carroll's column appears regularly in the Globe. His most recent book is " Crusade: Chronicles of an Unjust War ."