Ideas are powerful things, requiring not a studious contemplation but an action, even if it is only an inner action. Their acquisition obligates each man in some way to change his life, even if it is only his inner life. They demand to be stood for. They dictate where a man must concentrate his vision. They determine his moral and intellectual priorities. They provide him with allies and make him enemies. In short, ideas impose an interest in their ultimate fate which goes far beyond the realm of the merely reasonable.