Aristotle (384 BC-322 BC)

"It is the mark of an educated mind to be able to entertain a thought without accepting it."

"The roots of education are bitter, but the fruit is sweet."

"It is the mark of an instructed mind to rest assured with that degree of precision that the nature of the subject admits, and not to seek exactness when only an approximation of the truth is possible."

". . . the life of the mind is divine in comparison with mere human life. We should not follow popular advice and, being human, have only mortal thoughts, but should become immortal and do everything toward being the best in us."

"The least initial deviation from the truth is multiplied later a thousandfold."

"With regard to excellence, it is not enough to know, but we must try to have and use it."