There are people in this world who will never understand, say, the P?=NP problem no matter how much work they put into it. So to deny the above you'd have to say (along with Greg Egan) that there was some sort of threshold of intelligence akin to "Turing completeness" that only some of humanity were reached, but that once you reached it nothing was in principle beyond your comprehension. That doesn't seem impossible, but it's far from obvious.