“Not to be absolutely certain is, I think, one of the essential things in rationality.”

“a certain amount of boredom is...essential to a happy life”

“Dogmatism and skepticism are both, in a sense, absolute philosophies; one is certain of knowing, the other of not knowing. What philosophy should dissipate is certainty, whether of knowledge or ignorance.”

“The battle must be fought exactly as the battle of religious toleration was fought. And as in that case, so in this, a decay in the intensity of belief is likely to prove the decisive factor. While men were convinced of the absolute truth of Catholicism or Protestantism, as the case may be, they were willing to persecute on account of them. While men are quite certain of their modern creeds, they will persecute on their behalf. Some element of doubt is essential to the practice, thought not to the theory, of toleration.”

“Some care is needed in using Descartes' argument. "I think, therefore I am" says rather more than is strictly certain. It might seem as though we are quite sure of being the same person to-day as we were yesterday, and this is no doubt true in some sense. But the real Self is as hard to arrive at as the real table, and does not seem to have that absolute, convincing certainty that belongs to particular experiences.”

“The first effect of emancipation from the Church was not to make men think rationally, but to open their minds to every sort of antique nonsense”

“I do not myself think there is any superior rationality in being unhappy. The wise man will be as happy as circumstances permit, and if he finds contemplation of the universe painful beyond a point, he will contemplate something else instead.”