It is almost certain that Oxford-educated J. R. R. Tolkien recognized the correlation between his One Ring of the Dark Lord and the equally sinister ring of Gyges. Gyges the shepherd appears in a myth retold by Glaucon in Platos Republic (II, 359b-360b). Gyges was out shepherding in the Lydian countryside when an earthquake and simultaneous thunderstorm created a rift in the ground. Descending, Gyges found a bronze horse with openings leading to the interior. Inside was the body of a dead giant, naked but for a golden ring. Gyges put it on (like Tolkiens ring, this one must have adjusted to fit the finger of its new wearer, for Gyges was of normal stature) and found that when he rotated the face toward his palm he became invisible. He promptly used his invisibility to seduce the queen, murder the king, and become ruler of Lydia.
Glaucon told the story in an attempt to prove that every human, if rendered invisible to the law and society, will act to serve his own interests above those of all others. The main difference between Tolkiens ring and the one Glaucon describes is that the ring of Gyges is not evil or corruptive in itself. It simply provides invisibility; thereby giving man the power to act freely on the corruption already present in his own heart. The great irony of the ring of invisibility is that it exposes rather than conceals our true natures.