Diogenes Laërtius native of Laerte in Cilicia, was a biographer of ancient Greek philosophers. His Lives and Opinions of Eminent Philosophers, in ten books, is still extant and is an important source of information on the development of Greek philosophy. The period when he lived is not exactly known, but it is supposed to have been during the reigns of Septimius Severus and Caracalla.

Book 1: The Seven Sages

• Alcæus mentions Aristodemus in these lines:—
  ’T is money makes the man; and he who ’s none
  Is counted neither good nor honourable.
  • Thales, 8.

• Thales said there was no difference between life and death. "Why, then," said some one to him, "do not you die?" "Because," said he, "it does make no difference."
  • Thales, 9.

• When Thales was asked what was difficult, he said, "To know one’s self." And what was easy, "To advise another."
  • Thales, 9.

• He said that men ought to remember those friends who were absent as well as those who were present.
  • Thales, 9.

• The apophthegm "Know thyself" is his.
  • Thales, 13. Compare" "There are two sentences inscribed upon the Delphic oracle, hugely accommodated to the usages of man’s life: 'Know thyself', and 'Nothing too much'; and upon these all other precepts depend", Plutarch, Consolation to Apollonius.

• Writers differ with respect to the apophthegms of the Seven Sages, attributing the same one to various authors.
  • Thales, 14.

• Solon used to say that speech was the image of actions;... that laws were like cobwebs,—for that if any trifling or powerless thing fell into them, they held it fast; while if it were something weightier, it broke through them and was off.
  • Solon, 10.

• Solon gave the following advice: "Consider your honour, as a gentleman, of more weight than an oath. Never tell a lie. Pay attention to matters of importance."
  • Solon, 12.

• As some say, Solon was the author of the apophthegm, "Nothing in excess."
  • Solon, 16.

• Chilo advised, "not to speak evil of the dead."
  • Chilo, 2.

• Pittacus said that half was more than the whole.
  • Pittacus, 2.

• Heraclitus says that Pittacus, when he had got Alcæus into his power, released him, saying, "Forgiveness is better than revenge."
  • Pittacus, 3.

• One of his sayings was, "Even the gods cannot strive against necessity."
  • Pittacus, 4.

• Another was, "Watch your opportunity."
  • Pittacus, 7.

• Bias used to say that men ought to calculate life both as if they were fated to live a long and a short time, and that they ought to love one another as if at a future time they would come to hate one another; for that most men were bad.
  • Bias, 5.

• Ignorance plays the chief part among men, and the multitude of words.
  • Cleobulus, 4.

• The saying, "Practice is everything," is Periander’s.
  • Periander, 6.

Book 2: Socrates, his predecessors and followers

• Aristophanes turns Socrates into ridicule in his comedies, as making the worse appear the better reason.
  • Socrates, 5.

• Often when he was looking on at auctions he would say, "How many things there are which I do not need!"
  • Socrates, 10.

• Socrates said, "Those who want fewest things are nearest to the gods."
  • Socrates, 11.

• He said that there was one only good, namely, knowledge; and one only evil, namely, ignorance.
  • Socrates, 14.

• He declared that he knew nothing, except the fact of his ignorance.
  • Socrates, 16.

• Being asked whether it was better to marry or not, he replied, "Whichever you do, you will repent it."
  • Socrates, 16.

• He used to say that other men lived to eat, but that he ate to live.
  • Socrates, 16.

• Anarcharsis, on learning that the sides of a ship were four fingers thick, said that "the passengers were just that distance from death."
  • Anarcharsis, 5.

• He used to say that it was better to have one friend of great value than many friends who were good for nothing.
  • Anarcharsis, 5.

• The market is a place set apart where men may deceive each other.
  • Anacharsis, 5.

• It was a common saying of Myson that men ought not to investigate things from words, but words from things; for that things are not made for the sake of words, but words for things.
  • Myson, 3.

• Epimenides was sent by his father into the field to look for a sheep, turned out of the road at mid-day and lay down in a certain cave and fell asleep, and slept there fifty-seven years; and after that, when awake, he went on looking for the sheep, thinking that he had been taking a short nap.
  • Epimenides, 2.

• There are many marvellous stories told of Pherecydes. For it is said that he was walking along the seashore at Samos, and that seeing a ship sailing by with a fair wind, he said that it would soon sink; and presently it sank before his eyes. At another time he was drinking some water which had been drawn up out of a well, and he foretold that within three days there would be an earthquake; and there was one.
  • Pherecydes, 2.

• Anaximander used to assert that the primary cause of all things was the Infinite,—not defining exactly whether he meant air or water or anything else.
  • Anaximander, 2.

• Anaxagoras said to a man who was grieving because he was dying in a foreign land, "The descent to Hades is the same from every place."
  • Anaxagoras, 6.

• Aristippus being asked what were the most necessary things for well-born boys to learn, said, "Those things which they will put in practice when they become men."
  • Aristippus, 4.

• Aristippus said that a wise man’s country was the world.
  • Aristippus, 13.

Book 3: Plato

• Like sending owls to Athens, as the proverb goes.
  • Plato, 32.

• Plato affirmed that the soul was immortal and clothed in many bodies successively.
  • Plato, 40.

• Time is the image of eternity.
  • Plato, 41.

• That virtue was sufficient of herself for happiness.
  • Plato, 42.

• That the gods superintend all the affairs of men, and that there are such beings as dæmons.
  • Plato, 42.

• There is a written and an unwritten law. The one by which we regulate our constitutions in our cities is the written law; that which arises from customs is the unwritten law.
  • Plato, 51.

Book 4: The Academy

• Plato was continually saying to Xenocrates, "Sacrifice to the Graces."
  • Xenocrates, 3.

• Arcesilaus had a peculiar habit while conversing of using the expression, "My opinion is," and "So and so will not agree to this."
  • Arcesilaus, 12.

• Bion used to say that the way to the shades below was easy; he could go there with his eyes shut.
  • Bion, 3.

• Once when Bion was at sea in the company of some wicked men, he fell into the hands of pirates; and when the rest said, "We are undone if we are known,"—"But I," said he, "am undone if we are not known."
  • Bion, 3.

• Of a rich man who was niggardly he said, "That man does not own his estate, but his estate owns him."
  • Bion, 3.

• Bion insisted on the principle that "The property of friends is common."
  • Bion, 9.

• Old age is the harbor of all ills.
  • Bion, 47.

• Wealth is the sinews of affairs.
  • Bion, 48.

• The road to Hades is the easiest to travel.
  • Bion, 49.

• He has not acquired a fortune; the fortune has acquired him.
  • Bion, 50.

• Very late in life, when he was studying geometry, some one said to Lacydes, "Is it then a time for you to be learning now?" "If it is not," he replied, "when will it be?"
  • Lacydes, 5.

Book 5: The Peripatetics

• Aristotle was once asked what those who tell lies gain by it. Said he, "That when they speak truth they are not believed."
  • Aristotle, 9.

• The question was put to him, what hope is; and his answer was, "The dream of a waking man."
  • Aristotle, 9.

• He used to say that personal beauty was a better introduction than any letter; 18 but others say that it was Diogenes who gave this description of it, while Aristotle called beauty "the gift of God"; that Socrates called it "a short-lived tyranny"; Theophrastus, "a silent deceit"; Theocritus, "an ivory mischief"; Carneades, "a sovereignty which stood in need of no guards".
  • Aristotle, 9.

• On one occasion Aristotle was asked how much educated men were superior to those uneducated: "As much," said he, "as the living are to the dead."
  • Aristotle, 9.

• It was a saying of his that education was an ornament in prosperity and a refuge in adversity.
  • Aristotle, 9.

• He was once asked what a friend is, and his answer was, "One soul abiding in two bodies."
  • Aristotle, 9.

• Asked what he gained from philosophy, he answered, "To do without being commanded what others do from fear of the laws."
  • Aristotle, 9.

• The question was once put to him, how we ought to behave to our friends; and the answer he gave was, "As we should wish our friends to behave to us."
  • Aristotle, 9.

• He used to define justice as "a virtue of the soul distributing that which each person deserved."
  • Aristotle, 9.

• Another of his sayings was, that education was the best viaticum of old age.
  • Aristotle, 9.

• The chief good he has defined to be the exercise of virtue in a perfect life.
  • Aristotle, 13.

• He used to teach that God is incorporeal, as Plato also asserted, and that his providence extends over all the heavenly bodies.
  • Aristotle, 13.

• It was a favourite expression of Theophrastus that time was the most valuable thing that a man could spend.
  • Theophrastus, 10.

Book 6: The Cynics

• Antisthenes used to say that envious people were devoured by their own disposition, just as iron is by rust.
  • Antisthenes, 4.

• When he was praised by some wicked men, he said, "I am sadly afraid that I must have done some wicked thing."
  • Antisthenes, 4.

• When asked what learning was the most necessary, he said, "Not to unlearn what you have learned."
  • Antisthenes, 4.

• Diogenes would frequently praise those who were about to marry, and yet did not marry.
  • Diogenes, 4 (note that this is Diogenes of Sinope).

• "Bury me on my face," said Diogenes; and when he was asked why, he replied, "Because in a little while everything will be turned upside down."
  • Diogenes, 6.

• One of the sayings of Diogenes was that most men were within a finger’s breadth of being mad; for if a man walked with his middle finger pointing out, folks would think him mad, but not so if it were his forefinger.
  • Diogenes, 6.

• All things are in common among friends.
  • Diogenes, 6.

• "Be of good cheer," said Diogenes; "I see land."
  • Diogenes, 6.

• Plato having defined man to be a two-legged animal without feathers, Diogenes plucked a cock and brought it into the Academy, and said, "This is Plato’s man." On which account this addition was made to the definition,—"With broad flat nails."
  • Diogenes, 6.

• A man once asked Diogenes what was the proper time for supper, and he made answer, "If you are a rich man, whenever you please; and if you are a poor man, whenever you can."
  • Diogenes, 6.

• Diogenes lighted a candle in the daytime, and went round saying, "I am looking for a man."
  • Diogenes, 6.

• When asked what he would take to let a man give him a blow on the head, he said, "A helmet."
  • Diogenes, 6.

• Once he saw a youth blushing, and addressed him, "Courage, my boy! that is the complexion of virtue."
  • Diogenes, 6.

• When asked what wine he liked to drink, he replied, "That which belongs to another."
  • Diogenes, 6.

• Asked from what country he came, he replied, "I am a citizen of the world."
  • Diogenes, 6.

• When a man reproached him for going into unclean places, he said, "The sun too penetrates into privies, but is not polluted by them."
  • Diogenes, 6.

• Diogenes said once to a person who was showing him a dial, "It is a very useful thing to save a man from being too late for supper."
  • Menedemus, 3.

Book 7: The Stoics

• When Zeno was asked what a friend was, he replied, "Another I."
  • Zeno, 19.

• They say that the first inclination which an animal has is to protect itself.
  • Zeno, 52.

• One ought to seek out virtue for its own sake, without being influenced by fear or hope, or by any external influence. Moreover, that in that does happiness consist.
  • Zeno, 53.

• The Stoics also teach that God is unity, and that he is called Mind and Fate and Jupiter, and by many other names besides.
  • Zeno, 68.

• They also say that God is an animal immortal, rational, perfect, and intellectual in his happiness, unsusceptible of any kind of evil, having a foreknowledge of the universe and of all that is in the universe; however, that he has not the figure of a man; and that he is the creator of the universe, and as it were the Father of all things in common, and that a portion of him pervades everything.
  • Zeno, 72.

• But Chrysippus, Posidonius, Zeno, and Boëthus say, that all things are produced by fate. And fate is a connected cause of existing things, or the reason according to which the world is regulated.
  • Zeno, 74.

• Apollodorus says, "If any one were to take away from the books of Chrysippus all the passages which he quotes from other authors, his paper would be left empty."
  • Chrysippus, 3.

• One of the sophisms of Chrysippus was, "If you have not lost a thing, you have it."
  • Chrysippus, 11.

Book 8: Pythagoras and the Pythagoreans

• Pythagoras used to say that he had received as a gift from Mercury the perpetual transmigration of his soul, so that it was constantly transmigrating and passing into all sorts of plants or animals.
  • Pythagoras, 4.

• He calls drunkenness an expression identical with ruin.
  • Pythagoras, 6.

• Among what he called his precepts were such as these: Do not stir the fire with a sword. Do not sit down on a bushel. Do not devour thy heart.
  • Pythagoras, 17.

• In the time of Pythagoras that proverbial phrase Ipse dixit was introduced into ordinary life.
  • Pythagoras, 25.

Book 9: Uncategorized philosophers and Skeptics

• Xenophanes was the first person who asserted... that the soul is a spirit.
  • Xenophanes, 3.

• It takes a wise man to discover a wise man.
  • Xenophanes, 3.

• Protagoras asserted that there were two sides to every question, exactly opposite to each other.
  • Protagoras, 3.

• Nothing can be produced out of nothing.
  • Diogenes of Apollonia, 2.

• Xenophanes speaks thus:—
  And no man knows distinctly anything,
  And no man ever will.
  • Pyrrho, 8.

• Democritus says, "But we know nothing really; for truth lies deep down."
  • Pyrrho, 8.

• Euripides says,—
  Who knows but that this life is really death,
  And whether death is not what men call life?
  • Pyrrho, 8.

• The mountains, too, at a distance appear airy masses and smooth, but seen near at hand, they are rough.
  • Pyrrho, 9.

• If appearances are deceitful, then they do not deserve any confidence when they assert what appears to them to be true.
  • Pyrrho, 11.

• The chief good is the suspension of the judgment, which tranquillity of mind follows like its shadow.
  • Pyrrho, 11.

Book 10: Epicurus

• Epicurus laid down the doctrine that pleasure was the chief good.
  • Epicurus, 6.

• He alludes to the appearance of a face in the orb of the moon.
  • Epicurus, 25.

• Fortune is unstable, while our will is free.
  • Epicurus, 27.

Misattributed

• Just step aside for me to enjoy the sunshine.
  • Actually said by his namesake Diogenes of Sinope, when asked by Alexander the Great if there was anything he wanted.
  • Plutarch Parallel Lives, "Alexander", ch. 14, section 4.