Marcus Borg, like so many other theological liberals (although I must admit that Borg is so liberal that even a lot of theological liberals would disown him as such), claims God is ineffable.  During a recent debate between Borg and William Lane Craig, Craig pointed out that to say God is ineffable is to say that no human concept is applicable to God.  But since ineffability is a human concept, it doesn’t apply to God either.  This is self-refuting, and thus cannot be true.  Great point!