It comes down to the simple truth that what it is to be for the thing which knows (about) things cannot be anything like what it is to be for the things that are known. Furthermore, being can only be a question for the thing that knows (about) things, and not at all for the things known. To see that question is already a rare thing and cannot be reached by way of the mysteries of the things known - of which there are enough to claim all of one's attention.