Some men, not knowing the dissolution of mortal nature, suffer wretchedly throughout their lifetime from distress and fear because of their consciousness of the evildoing in their lives, making false speculations about the time after death.Few believe that Democritus was doing anything more than taking up a usage for the word that was popular and common in his time. Synoida literally meant "to know in common with" and was often used for knowledge about which you could bear witness for or against another person. In the sense of conscience, you are bearing witness for or against yourself.
The closest any early Greek comes to the idea of a good conscience is the historian Xenophon (430-354) who bears witness within himself that he does good works: "We know with ourselves that we began as children and still continue in the practice of noble and good works."
All of the other early Greek references to "know with ourselves" are associated with an internal witness to something bad. A fragment from the dramatist Menander (342-291 BCE) suggests that, in the world of politics, anyone who bears witness within himself, no matter how brave, will be terrorized by what he knows. The historian Polybius (203-120 BCE) writes that "there is no witness as fearful nor accuser as terrible as the conscience which dwells in every man’s soul."
One of the earliest portrayals of the effects of conscience came from the tragedian Euripedes (480-406 BCE) in Orestes, a play about a son who was advised by the god Apollo to avenge the death of his father by killing his mother who murdered him:
Orestes: Here I am, the murderer of my wretched mother.Philo of Alexandria (20 BC – 50 AD), a Hellenistic Jewish philosopher, describes conscience as something that wages war within the soul:
Menelaus: I have heard, spare your words; evils should be seldom spoken.
Orestes: I will be sparing; but the deity is lavish of woe to me.
Menelaus: What ails you? What is your deadly sickness?
Orestes: My conscience; I am aware of having done terrible things.
Come now, if you please, and with your reason look into the mind of the man who is about to swear to a falsehood; and you will see that it is not tranquil, but full of disorder and confusion, accusing itself, and enduring all kinds of insolence and evil speaking; for the conscience which dwells in, and never leaves the soul of each individual, not being accustomed to admit to itself any wicked thing, preserves its own nature always such as to hate evil, and to love virtue, being itself at the same time an accuser and a judge; being roused as an accuser it blames, impeaches, and is hostile; and again as a judge it teaches, admonishes, and recommends the accused to change his ways, and if he be able to persuade him, he is with joy reconciled to him, but if he be not able to do so, then he wages an endless and implacable war against him, never quitting him neither by day, nor by night, but pricking him, and inflicting incurable wounds on him, until he destroys his miserable and accursed life.The historian Plutarch (46-120 AD), a native of Greece who became a Roman citizen, described the conscience as like an ulcer:
Like an ulcer in the flesh. It implants in the soul a remorse which never ceases to wound and to goad it. Any other pain can be reasoned away, but this remorse is inflicted by reason, on the soul which is so racked with shame, and self-chastised. For just as those overcome by shivering fits, or burning with fever, suffer worse and are in greater distress than those who suffer the equivalent, but external, heat or cold, so the pains which come as it were from without and by chance are more easy to bear. But the cry "None other is to blame for this but myself" coming from within upon the wicked man's own sins, makes his sufferings yet harder to bear.One of the most widely quoted statements about the Greek conscience, erroneously attributed to the Stoic philosopher Epictetus (55-135 AD) by the historian of music Marcus Meibomius (1630-1710), is from an unknown author and dates from around 90 AD:
When we were children our parents handed us over to a nursery-slave who should watch over us everywhere lest harm befall us. But when we are grown up, God hands us over to the conscience implanted in us, to protect us. Let us not in any way despise its protection, for should we do so we shall be both ill-pleasing to God and have our own conscience as an enemy.