“Even if all knowledge could be found in books, where it is mixed in with so many useless things and confusingly heaped in such large volumes, it would take longer to read those books than we have to live in this life and more effort to select the useful things than to find them oneself”

“Dubium sapientiae initium (Doubt is the origin of wisdom).”

“To live without philosophizing is in truth the same as keeping the eyes closed without attempting to open them.”

“He cannot be a deceiver, since the light of nature teaches us that fraud and deception necessarily proceed from some defect.”

“There is nothing more ancient than the truth.”

“You just keep pushing. You just keep pushing. I made every mistake that could be made. But I just kept pushing.”

“If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.”

“Except our own thoughts, there is nothing absolutely in our power.”

“I suppose therefore that all things I see are illusions; I believe that nothing has ever existed of everything my lying memory tells me. I think I have no senses. I believe that body, shape, extension, motion, location are functions. What is there then that can be taken as true? Perhaps only this one thing, that nothing at all is certain.”

“Common sense is the most widely shared commodity in the world, for every man is convinced that he is well supplied with it.”