Since the first inauguration in 1789, each president has referenced God in his inaugural address. After taking the oath of office, George Washington ad-libbed the final words, "So help me God." Every president since has done the same in the oath.
The question has never been whether religious language will be used in presidential inaugurals, but how. In perhaps the most famous, Lincolns second inaugural address, God was invoked not to bless the nation, or give any triumphal comfort to either side in the Civil War, but rather to call the nation to penitence. In doing so, he showed a preference for humble reflection over easy certainty, accountability over blessing, repentance over confidence. That was missing in George W. Bushs second inaugural, which was rather full of a religious sense of both confidence and mission.
For an evangelical Christian, George W. Bush does not seem to have a well-developed sense of sin - at least as far as the nation is concerned. In his speech, President Bush expressed a far-reaching commitment to "liberty" and "the force of human freedom" in the world - values that most Americans, religious or not, would readily affirm. The president has often rightly acknowledged that "freedom" is a gift from God, not the possession of any nation. But his remarkable speech announced that the role of deciding if, when, and where freedom will be defended belongs to the United States of America; America is on a religious mission to protect freedom, and George Bush is freedoms vicar.