[Lurking Libertarian]

The standard in this country for God's-honest-truth is the Bible.

The men who wrote the Constitution didn't think so; for example, Article VI says that "all executive and judicial Officers... shall be bound by Oath or Affirmation to support this Constitution..."

[so_real]

If I recall correctly, an affirmation was permitted for the benefit of the Quaker population who, by virtue of Jesus' call to 'swear not at all' during the Sermon on the Mount, held themselves to a high standard of truthfulness at all times. They felt it more Christian to simply affirm their willingness to speak only the truth, than to make a formal oath of it. Either way, whether you take an oath with your hand on it, or make an affirmation because of the Sermon on the Mount printed in it, the Bible remains the standard in this country for God's-honest-truth.