stairwell accompaniment:

It is...an idea which I would always have theoretically admitted—the idea that I, or any mortal at any time, may be utterly mistaken as to the situation he is really in. Five senses; an incurably abstract intellect; a haphazardly selective memory; a set of preconceptions and assumptions so numerous that I can never examine more than a minority of them—never become even conscious of them all. How much of total reality can such an apparatus let through?--C.S. Lewis, A Grief Observed