“Although this was not a comforting point of view, he did not reject it, because it coincided with one of his basic beliefs: that a man must at all costs keep some part of himself outside and beyond life. If he should ever for an instant cease doubting, accept wholly the truth of what his senses conveyed to him, he would be dislodged from the solid ground to which he clung and swept along with the current, having lost all objective sense, totally involved with existence.”