From "on the Duties of the Clergy"
I NEED not imagine a great chasm in the earth, which had been loosened by heavy rains, and had afterwards burst asunder, as Plato does. For he makes Gyges descend into that chasm, and to meet there that iron horse of the fable that had doors in its sides. When these doors were opened, he found a gold ring on the finger of a dead man, whose corpse lay there lifeless. He desiring the gold took away the ring. But when he returned to the king's shepherds, to whose number he belonged, by chance having turned the stone inwards towards the palms of his hands, he saw all, yet was seen by none. Then when he turned the ring to its proper position, he was again seen by all. On becoming conscious of this strange power, by the use of the ring he committed adultery with the queen, killed the king, and took possession of the kingdom after slaying all the rest, who he thought should be put to death, so that they might be no hindrance to him. Give, says Plato, this ring to a wise man, that when he commits a fault he may by its help remain unnoticed; yet he will be none the more free from the stain of sin than if he could not be hid. The hiding-place of the wise lies not in the hope of impunity but in his own innocency. Lastly, the law is not laid down for the just but for the unjust [cf. I Tim. 1.9]. For the just has within himself the law of his mind, and a rule of equity and justice. Thus he is not recalled from sin by fear of punishment, but by the rule of a virtuous life.
Cf. Plato : The Ring of Gyges / at POLITEIA Whitehead, Wide opportunities for experience Russell Lowell, Fecundating minds Emerson, Disclosing in every fact a germ of expansion W.K.C. Guthrie, Life of Plato and philosophical influences * Plato home, Anthology, Complete works, Concepts
Reference address : http://www.ellopos.net/elpenor/greeks-us/ambrose-gyges.asp