"A life without investigation is not worth living."

"There are three arts which are concerned with all things. One which uses, another which makes, and a third which imitates them."

"The learning and knowledge that we have, is, at the most, but little compared with that of which we are ignorant."

"There is nothing I like better than conversing with aged men. For I regard them as travelers who have gone a journey which I too may have to go, and of whom I ought to inquire whether the way is smooth and easy or rugged and difficult. Is life harder toward the end, or what report do you give it?"

"Those who don't know must learn from those who do."

"Until philosophers are kings, or the kings and princes of this world have the spirit and power of philosophy, and political greatness and wisdom meet in one, and those commoner natures who pursue either to the exclusion of the other are compelled to stand aside, cities will never have rest from their evils — no, nor the human race, as I believe — and then only will this our State have a possibility of life and behold the light of day."

"Certainly we shall have to look to ourselves, and try to find someone who will help in some way or other to improve us."

"When there is an income tax, the just man will pay more and the unjust less on the same amount of income."

"The love, more especially, which is concerned with the good, and which is perfected in company with temperance and justice, whether among gods or men, has the greatest power, and is the source of all our happiness and harmony, and makes us friends with the gods who are above us, and with one another."

"Beauty of style and harmony and grace and good rhythm depend on simplicity I mean the true simplicity of a rightly and nobly ordered mind and character, not that other simplicity which is only a euphemism for folly."