"The question of how the eye works - that is, what happens when a photon of light first impinges on the retina - simply could not be answered at that time"

"Questions are never indiscreet, answers sometimes are"

"Question everything. Learn something. Answer nothing"

"Do not waste your time on Social Questions. What is the matter with the poor is Poverty; what is the matter with the rich is Uselessness"

"Youth is not a question of years: one is young or old from birth"

"The question is not, "Can they reason?" nor, "Can they talk?" but rather, "Can they suffer?""

"The power to question is the basis of all human progress"

"Who questions much, shall learn much, and retain much"

"If the present Congress errs in too much talking, how can it be otherwise in a body to which the people send one hundred and fifty lawyers, whose trade it is to question everything, yield nothing, and talk by the hour?"

"It is not enough to be busy. So are the ants. The question is: What are we busy about?"

"The only interesting answers are those that destroy the questions"