I see where the Volokh-Prager debate over the propriety of taking an oath of office on a Koran has migrated to TV. Ellison seems to be a pretty despicable character, and it's a damn shame the voters in his district couldn't find someone else to give that sinecure to, but that said, I think Prager's wrong on this one.
First of all, let's dispense with the "religious test" stuff that Reynolds brings up. This isn't a legal argument, it's a political-symbolic one, and no one's suggesting that Ellison not be allowed to take office because he's a Muslim. In any event, the Islamist apologists are always talking about how the Bible is holy to them, too.
That said, as a couple of Orthodox Jews who called into his show Tuesday said, the book you take the oath on isn't for the benefit of the country, it's for your own. You put your hand on a book you believe in, and Prager's straw-man argument that you have to believe every word is the literal truth is off the mark. Reform Jews believe the Hebrew Bible is holy, they just believe it was written by men, not God.
But I think it's possible to win this argument even on Prager's terms. Washington, Madison, Monroe, Franklin, and other Framers were Freemasons. I'm a Freemason. The rule is that the oath of membership in the society is taken on whatever book is deemed holy to the person taking the oath. To claim that this understanding of what an oath means is incorrect is to invalidate the understanding that the Framers had of oaths, the very Framers that Prager is seeking to venerate by insisting that Ellison use a Bible.