The too perfect security of the Upper-worlders had led them to a slow movement of degeneration, a general dwindling in size, strength, and intelligence.
Sometimes it can seem that history is turning in a wide arc, toward an unknown shore. Yet the destination of history is determined by human action, and every great movement of history comes to a point of choosing.
The future of a movement is conditioned by the fanaticism, yes, the intolerance, with which its adherents uphold it as the sole correct movement, and push it past other formations of a similar sort.