I had a strange dream, or half-waking vision, not long ago. I found myself at the top of a mountain in the mist, feeling very pleased with myself, not just for having climbed the mountain, but for having achieved my life's ambition, to find a way of answering moral questions rationally. But as I was preening myself on this achievement, the mist began to clear, and I saw that I was surrounded on the mountain top by the graves of all those other philosophers, great and small, who had had the same ambition, and thought they had achieved it. And I have come to see, reflecting on my dream, that, ever since, the hard-working philosophical worms have been nibbling away at their systems and showing that the achievement was an illusion. True, their skeletons, indigestible to worms, remained, and were surprisingly similar to one another. But I was led to think again about what one can, and what one cannot, achieve in this direction.