What 'So Help Me God' Meant to George Washington

Did George Washington add the words “so help me God” to the constitutionally prescribed oath of office when he was sworn in as president on April 30, 1789? I’ve always thought so, and when discussing Kentucky clerk Kim Davis’s misinterpretation of her oath of office last week, I wrote that the U.S. Constitution doesn't include the words but that Washington “famously added them.” Immediately I received an e-mail citing an essay that claims this widely held view was in fact a myth, unsubstantiated by contemporary historical evidence and derived from a doubtful childhood memory by Washington Irving. I read the essay, and then found counterarguments on the web and in a good old-fashioned book.

So what's the truth? And why should we care, other than historical accuracy, which is always desirable and never perfectly attainable? I've done some research, so let me try to offer a measured answer -- and then suggest the lesson for today's debates about religion and government, often in the context of gay marriage.