"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."

"Never attribute to malice that which can be adequately explained by stupidity."

"No one in this world, so far as I know — and I have researched the records for years, and employed agents to help me — has ever lost money by underestimating the intelligence of the great masses of the plain people. Nor has anyone ever lost public office thereby."