You can't think of being or attend to it because to do so would make of it an object in some sense, but you are able to question it. This is an anomaly of thought, or rather an anomalous comportment, it ought not to be possible - and perhaps it is not possible and that's precisely what is so questionable. As if it were a vestige of creation, like the navel. But since it is an irreducible anomaly of experience it must be that experience is not what it appears to be and the only reality is in that questionable residue. (In the same way that a tiny anomaly in physical measurement completely overturned physics so that the anomaly is now the theoretical and ontological prior.) This residue is almost entirely erased, in fact it isn't even suspected most of the time, but it overturns everything. Experience is the way it appears to be just in order to keep this reality concealed.