W.H.R.Rivers, Instinct and the Unconscious — Chapter II. The Unconscious (1920)
“ I can in imagination go downstairs into a kitchen in a basement and I can go upstairs towards the upper door, but when I reach the top of the stairs I come to the absolutely unknown, an unknown far more complete than is the case with any house occupied more recently, where I have some idea of the topography, though this is inexact and vague. For more than two years I have been attempting, by means which have succeeded in evoking other early experience, to penetrate into the mysterious unknown of the upper storey. ”
