"I believe that you believe it" is a Stock Phrase that can occur in several different contexts. For example: Or... Either way, Bob's not accusing Alice of lying, but he's still not quite as understanding as Alice might hope. He's implying (in the former case) that she's over-imaginative, paranoid, even crazy, or (in the latter) that she doesn't know herself as well as he does or that she lacks follow-through. In any case, Alice usually finds it pretty insulting, even though in most cases Bob means well by it. Related to Damned By Faint Praise Trivially Obvious, Theory Before Phenomenon. Not related to believing in someone who believes in you.