A committee in the U.S. House of Representatives considered making the words “So help me God” optional for witnesses who appear before it, but quickly dropped the idea after criticism from conservatives.

Courtroom oaths to 'tell the whole truth' have a long lineage in Western culture – they’re mentioned in the writings of the Roman statesman Cicero. It’s unclear when the religious element crept in – perhaps during the Middle Ages – but more and more courts are making secular alternatives available for those who’d rather not, for whatever reason, say the words 'So help me God.'

Sure, members of Congress can use a Bible to take the oath of office, but they’re not required to use anything. They can just take the oath if they choose. Or they can swear on another book.