“They had applied their doubts to the very head that had introduced doubt as a tool for advancing knowledge. And in the end they gave the head a nod.”

“We are graced with a godlike ability to transcend time and space in our minds but are chained to death.”

“Is there any knowledge in the world which is so certain that no reasonable man could doubt it?”

“And if there were a God, I think it very unlikely that He would have such an uneasy vanity as to be offended by those who doubt His existence”

“Because a doubt is not a denial. Doubt is a powerful tool, and it should be applied to history.”

“Philosophy, though unable to tell us with certainty what is the true answer to the doubts which it raises, is able to suggest many possiblities which enlarge our thoughts and free them from the tyranny of custom. Thus, while diminishing our feeling of certainty as to what things are, it greatly increases our knowledge as to what the may be; it removes the somewhat arrogant dogmatism of those who have never travelled into the region of liberating doubt, and it keeps alive our sense of wonder by showing familar things in an unfamilar aspect”

“The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt.”