At noon on Jan. 20, Barack Obama will place his left hand on the Lincoln Bible, a velvet-bound tome purchased by a Supreme Court clerk for the Great Emancipator's swearing in. He will raise his right hand and repeat after Chief Justice John Roberts these words from Section 1 of the Second Article of the U.S. Constitution: "I do solemnly swear (or affirm) that I will faithfully execute the office of President of the United States, and will to the best of my ability, preserve, protect and defend the Constitution of the United States."
As a speech, it's short and to the point. As a symbol of the duties of public office, it's momentous. Bibles have been used to consecrate oaths for hundreds of years: they've had a role in the coronation of British monarchs since the 11th century. Swearing on Scripture in courts of law dates back to 300 B.C.
While most presidential oaths have been administered by the Chief Justice--Roger Taney swore in seven Commanders in Chief, a record--it's not required. Calvin Coolidge's father, a notary public, presided over one of his son's two oaths, in 1923. Presidents can choose to affirm instead of swear (although only one has: the devout Franklin Pierce). And most have added "So help me God" at the end, as George Washington is believed to have done, though historians now dispute it. Several Presidents, including George W. Bush, were sworn in on the Washington Bible, a 10-lb. volume belonging to a New York Freemasons' society. John Quincy Adams, to keep a barrier between church and state, was sworn in on a book of U.S. laws. Harry S Truman used two Bibles in 1949--one, a gift from friends; the other, the one he used in his 1945 Inauguration. No matter what book or how many, an oath is an oath: the swearer is officially considered President from that moment on.