In fact, opposition is about the only incentive we have to practice reason and tolerance. Unless our ideas are questioned, they become part of the furniture of eterity. It is only by incessant criticism, by constant rubbing in of differences, that any of our ideas remain human and decent. The easy way is when we are not opposed. That enables us to be dogmatic, and to regard whatever we happen to believe as of sovereign value.
To keep a faith pure, man had better retire to a monastery. Where all think alike, no one thinks very much. But whatever he does think, he can think with all his soul. It is at the cross-roads that skepticism is born, not in a hermitage. Without contact and friction, without experience, in short, our animal loyalties are supreme. Thought is not made in a vacuum, nor created out of likeness. It requires travel and shipping and the coming and going of strangers to impregnate a civilization. That is why thought has flourished in cities which lie along the paths of communication. Nineveh, Athens, Alexandria, Rome, Venice, the Hansa towns, London, Paris—they have made ideas out of the movement and contact of many people. Men are jostled into thought. Left alone they spin the same thread from the same dream. A community which is self-contained and homogeneous and secluded is intellectually deaf, dumb, and blind. It can cultivate robust virtue and simple dogmatism, but it will not invent or throw out a profusion of ideas.