He announces that we deny the existence of the external world. Such a man is not really criticizing our doctrine but only his own misconceptions of it. Therefore we are not called upon to answer him. If we do put pen to paper, it is an act of grace in recognition of the difficulty of comprehending this doctrine, not as an act of controversy in refutal of absurd ideas upon which we cannot waste our time.
-- Notebooks Category 12: Reflections > Chapter 5: The Literary Work > # 111