"I say quite deliberately that the Christian religion, as organized in its churches, has been and still is the principal enemy of moral progress in the world."

"To fear love is to fear life, and those who fear life are already three parts dead."

"I feel I shall find the truth on my deathbed and be surrounded by people too stupid to understand—fussing about medicines instead of searching for wisdom."

"It is easy to imagine a world where the sun never sets, and yet the inhabitants are miserable."

"To teach how to live without certainty, and yet without being paralysed by hesitation, is perhaps the chief thing that philosophy, in our age, can still do for those who study it."