When one writes philosophy, and not just then, of course, but philosophy has its peculiar poignancy, one shows what one understands but also, and unawares, what one has so far failed to understand. Unfortunately, as one grows older a certain complacency sets in as one repeats one's settled insights and gives less attention even to the possibility that there might be things beyond one's reach ... of course one would acknowledge that no doubt there are such things, if the question was raised, but it is not active in one's thoughts, because one has lost the sense of being at the dangerous edge of sense and comprehension.