The physical change in the thickness of walls since the Middle Ages could be shown in a diagram. In the fourteenth century each house was a fortress. Man spent the major portion of his day in them, in secret and well-defended solitude. That solitude, working on the soul hour after hour, forged it, like a transcendent blacksmith, into a compact and forceful character. Under its treatment, man consolidated his individual destiny and sallied forth with impunity, never yielding to the contamination from the public. It is only in isolation that we gain, almost automatically, a certain discrimination in ideas, desires, longings, that we learn which are ours, and which are anonymous, floating in the air, falling on us like dust in the street.