"He that makes experiments, must not be tied to any particular opinion."

"I have always preferred the plainness of truth to the ornaments of eloquence."

"I have often thought that the greatest wisdom consists in knowing our own ignorance."

"I am not ashamed to confess that I have learned more from observation than from all the books I have ever read."

"I once kept a viper in a sealed glass jar until it died, to observe the effects of air deprivation."