Democritus was born at Abdera, Thrace, sometime around 458 BCE. He was described as well traveled, probably visiting Babylon, Egypt, and Ethiopia, and perhaps India. He appears to have spent all of his time on scientific and philosophical studies, teaching, and writing— some 60 works have been listed. Of his voluminous writings, only a few fragments of his ethical theory remain. But these fragments and the descriptions by other writers of his atomic theory put him among the foremost thinkers of his time.

Aristoxenus wrote that Plato wanted to burn all the works of Democritus, but could not do so because the books were already in wide circulation. Failing this, he avoided any mention of Democritus in his own writings. Certainly, Socrates’ brand of argument might not have fared well against Democritus, who was described by Timon as "the guardian of discourse, a keen witted disputant".

Democritus’s theory of the atomic nature of the physical world, developed from that of Leucippus, is known only through the works of critics of the theory such as Aristotle and Theophrastus. It resolved the question of how a world evidently in a state of flux could nevertheless have an underlying nature that was eternal and unchanging. By positing infinitely small things that remained the same but formed different combinations with each other, Leucippus initially, and Democritus in greater detail, managed to answer the question in a way that has been subject to increasingly successful elaboration ever since. One can trace the physical theory of atoms through Epicurus, Lucretius, and Galileo to modern times.

Democritus was an original thinker in ethical theory, setting high standards of personal integrity and social responsibility, without invoking supernatural sanctions. Indeed, it is probably the banishment of supernatural and non-material agencies by atomic theory that upset Plato so much and subsequently led to its neglect for over a thousand years. Democritus argued that one’s own consciousness of right and wrong should prevent one from doing anything shameful, not the fear of breaking the law or being vilified by public opinion. He thought that men fashioned an image of Chance as an excuse for their own stupidity, because chance rarely conflicts with intelligence and most things in life can be set in order by an intelligent farsightedness. With regard to aesthetics he is said to have remarked that there is no poetry without madness.

Hermippus wrote that when Democritus was nearing his end, his sister was upset because his death could prevent her from worshipping at the three-day festival of Thesmophoria. Democritus told her not to worry, and kept himself alive by inhaling the fresh smell of baked loaves until the end of the festival, when he relinquished his life without pain. Hipparchus wrote that Democritus was then in his 109th year.

The extracts below have been assembled out of surviving fragments, and do not correspond to any extant work. It represents what he might have said if asked to give a few off-the-cuff remarks.

1 Happiness does not dwell in flocks of cattle or in gold. Happiness, like unhappiness, is a property of the soul. And it is right that men should value the soul rather than the body; for perfection of soul corrects the inferiority of the body, but physical strength without intelligence does nothing to improve the mind. Men find happiness neither by means of the body nor through possessions, but through uprightness and wisdom.

2 People are fools who yearn for what is absent, but neglect what they have even when it is more valuable than what has gone. The hopes of right-thinking men are attainable, but those of the unintelligent are impossible.

3 The best way for a man to lead his life is to have been as cheerful as possible and to have suffered as little as possible. This could happen if one did not seek one’s pleasures in mortal things. The right-minded man is he who is not grieved by what he has not, but enjoys what he has. He is fortunate who is happy with moderate means, unfortunate who is unhappy with great possessions.

4 One should realize that human life is weak and brief and mixed with many cares and difficulties, in order that one may care only for moderate possessions, and that hardship may be measured by the standard of one’s needs. Cheerfulness or well-being is created in man through a harmonious life and moderation of enjoyment. Excess and want are forever changing and cause great disturbance in the soul. Souls that are stirred by great disturbances are neither stable nor cheerful. Therefore one must keep one’s mind on what is attainable, and be content with what one has, paying little heed to things envied and admired, and not dwelling on them in one’s mind.

Rather, you should consider the lives of those in distress, reflecting on their intense sufferings, in order that your own possessions and condition may seem great and enviable, and you may, by ceasing to desire more, cease to suffer in your soul. . . . If you keep to this way of thinking, you will live more serenely, and will expel those not-negligible curses in life—envy, jealousy and spite.

5 The cheerful man, who is impelled towards just and lawful actions, rejoices by day and by night, and is strong and free from care. But the man who ignores justice, and does not do what he ought, finds all such things disagreeable when he remembers any of them, and he is afraid and torments himself.

6 One must not respect the opinion of other men more than one’s own; nor must one be more ready to do wrong if no one will know than if all will know. One must respect one’s own opinion most, and this must stand as the law of one’s soul, preventing one from doing anything improper.

7 The man who wishes to have serenity of spirit should not engage in many activities, either private or public, nor choose activities beyond his power and natural capacity. He must guard against this, so that when good fortune falls on him and tempts him to excess by means of false appearances, he must value it little, and not attempt things beyond his powers. A reasonable fullness is better than over-fullness.

8 It is hard to fight desire; but to control it is the sign of a reasonable man. Violent desire for one thing blinds the soul to all others. Immoderate desire is the mark of a child, not a man. If your desires are not great, a little will seem much to you; for small appetite makes poverty equivalent to wealth.

9 The criterion distinguishing the advantageous from the disadvantageous is enjoyment and lack of enjoyment. People are fools who live without enjoyment of life. One should choose not every pleasure, but only that concerned with the beautiful. The great pleasures come from the contemplation of noble works. What a poet writes with enthusiasm and divine inspiration is most beautiful. Beautiful objects are wrought by study through effort, but ugly things are reaped automatically without toil. The great pleasures come from the contemplation of noble works.

Of pleasures, those that come most rarely give the greatest enjoyment. Thrift and fasting are beneficial; so too is expenditure at the right time. But to recognize this is the function of a good man. A life without festival is a long road without an inn.

10 Pleasure and absence of pleasure are the criteria of what is profitable and what is not. Accept no pleasure unless it is beneficial. Moderation multiplies pleasures, and increases pleasure. If one oversteps the due measure, the most pleasurable things become most unpleasant. The brave man is not only he who overcomes the enemy, but he who is stronger than pleasures. Some men are masters of cities, but are enslaved to women. Untimely pleasures produce unpleasantness.

11 All who derive their pleasures from the stomach, overstepping moderation in eating or drinking or sexual pleasure, have pleasures that are but brief and short-lived—only while they are eating and drinking—but pains that are many. For this desire is always present for the same things, and when people get what they desire, the pleasure passes quickly, and they have nothing good for themselves except a brief enjoyment; and then again the need for the same things returns.

12 To live badly is not to live badly, but to spend a long time dying. People are fools who yearn for long life without having pleasure in long life. People are fools who hate life and yet wish to live through fear of death. Men who shun death pursue it.

13 Some men, not knowing about the dissolution of mortal nature, but acting on knowledge of the suffering in life, afflict the period of life with anxieties and fears, inventing false tales about the period after the end of life. Few men of reason have beat the air with their hands and exclaimed, "Zeus considers all things and he knows all and gives and takes away all and is king of all."

14 Men ask in their prayers for health from the gods, but do not know that the power to attain this lies in themselves. By doing the opposite of what they should do, through lack of control, they themselves become the betrayers of their own health to their desires. The things needed by the body are available to all without toil and trouble. But the things which require toil and trouble and which make life disagreeable are not desired by the body but by an ill-constitution of the mind.

15 Good breeding in cattle depends on physical health, but in men it depends on a well-formed character. Those whose character is well-ordered have also a well-ordered life. Well-ordered behavior consists in obedience to the law, the ruler, and the man wiser than oneself.

16 The man who employs exhortation and persuasion will turn out to be a more effective guide to virtue than he who employs law and compulsion. For the man who is prevented by law from wrongdoing will probably do wrong in secret. On the other hand, the man who is led towards duty by persuasion will probably not do anything untoward either secretly or openly. Therefore the man who acts rightly through understanding and knowledge becomes at the same time brave and upright.

17 Noble deeds are recognized and emulated by those of natural good disposition. One should emulate the deeds and actions of virtue, not the words. The worthy and the unworthy man are to be known not only by their actions, but also by their wishes. When inferior men censure, the good man pays no heed.

18 One must either be good, or imitate a good man. It is a bad thing to imitate the bad and not even to wish to imitate the good. More men become good through practice than by nature. Do not say or do what is base, even when you are alone. Learn to feel shame in your own eyes much more than before others. Repentance for shameful deeds is salvation in life.

19 Virtue does not consist of avoiding wrongdoing, but in having no wish to do wrong. It is a great thing, when one is in adversity, to think of duty. Refrain from crimes not through fear but through duty. It is noble to prevent the criminal; but if one cannot, one should not join him in crime.

20 Continuous association with base men increases a disposition to crime. One must avoid even speaking of evil deeds. It is easy to either praise or blame what one should not, but both are the marks of a corrupt character. Neither can fine speech cover up base action, nor can good action be injured by calumny.

21 The man who loves nobody is, I think, loved by no one. Life is not worth living for the man who has not even one good friend. Similarity of outlook creates friendship. The man whose tested friends do not stay long with him is bad-tempered. The censorious are also not well-fitted for friendship. Many avoid their friends when they fall from wealth to poverty. In prosperity it is easy to find a friend, in adversity nothing is so difficult.

22 Many who seem friendly are not so, and those who do not seem so, are. Not all one’s relatives are friends, but only those who agree with us about what is advantageous. The enmity of relatives is much worse than that of strangers.

The friendship of one intelligent man is better than that of all the unintelligent.

23 Believe not everything, but only what is proven: the former is foolish, the latter the act of a sensible man. Fools are shaped by the gifts of chance, but those who understand these things, by the gifts of wisdom.

24 One should practice much-sense, not much-learning. Many much-learned men have no intelligence.

25 There are two ways of knowledge, one genuine, one imperfect. To the latter belong all the following: sight, hearing, smell, taste, touch. The real is separated from this. When the imperfect can do no more—neither see more minutely, nor hear, nor smell, nor taste, nor perceive by touch with greater clarity — and a finer investigation is needed, then the genuine way of knowledge comes in as having a tool for distinguishing more finely.

26 It has often been demonstrated that we do not grasp how each thing is or is not. Sweet exists by convention, bitter by convention, color by convention. Atoms and void alone exist in reality. . . We know nothing accurately in reality, but only as it changes according to the bodily condition, and the constitution of those things that flow upon the body and impinge upon it. It will be obvious that it is impossible to understand how in reality each thing is.

27 Imperturbable wisdom is worth everything. To a wise man, the whole earth is open; for the native land of a good soul is the whole earth. Medicine heals diseases of the body, wisdom frees the soul from passions. Neither skill nor wisdom is attainable unless one learns. Beautiful objects are wrought by study through effort, but ugly things are reaped automatically without toil.

28 Nature and instruction are similar; for instruction transforms the man, and in transforming, creates his nature. Education is an ornament for the prosperous, a refuge for the unfortunate. The hopes of the educated are better than the wealth of the ignorant.

29 There is an intelligence of the young, and an unintelligence of the aged. It is not time that teaches wisdom, but early training and natural endowment. It is possible without spending much of one’s money to educate one’s children, and so to build round their property and their persons a fortification and a safeguard. If children are left free to not study, they cannot learn letters or music or gymnastic, nor that which above all things embraces virtue— reverence. For it is precisely from these studies that reverence usually grows.

30 Frivolity in an educator of youth is the worst of all things, for it breeds those pleasures from which wickedness comes.

31 Those who praise the unintelligent do them great harm. Fame and wealth without intelligence are dangerous possessions. The hopes of the unintelligent are senseless. For the foolish, not reason but advantage is the teacher. The foolish learn sense through misfortune.

He who tries to give intelligent advice to one who thinks he has intelligence, is wasting his time.