Visually the most compelling symbol based on the human body, often used to represent the omniscience of sun gods and, in early Christianity, God the Father (a single eye) or the Trinity (an eye within a triangle).
The Egyptian wedjat, a painted eye with a link spiraling below it (taken from the facial markings of some hawks), is the emblem of the falcon sky-god, Horus and is a symbol not only of his all-seeing power but of cosmic wholeness. In Western symbolism, the right eye is active and solar; the left passive and lunar (a system reversed in Eastern tradition). Egyptian myth said that the moon eye of Horus had been restored after its destruction in a battle with Set, a story that accounts for the popularity of the wedjat as a protective device on amulets. Eyes were also painted or carved on Egyptian tombs to assist the dead. Winged eyes in Egyptian iconography represent north and south.
The occult third eye, sometimes called the ‘eye of the heart’, symbolizes the eye of spiritual perception, associated with the power of Shiva and the synthesizing element of fire in Hinduism, with the inner vision in Buddhism, and with superhuman clairvoyance in Islam. Although depicted on the forehead of Shiva, it is an inner eye. Its antithesis is the ‘evil eye’ which, in Islamic thought, is a symbol of the destructive force of envy. The Gorgon Medusa whose gaze could turn men to stone was an earlier Greek symbol of the evil eye. Perseus used a mirror to aim the blow that killed her, and eye talismans (still hung above doorways in Turkey) serve a similar deflecting function.
In medieval Europe, the horseshoe was though to be particularly effective against the evil eye of witchcraft or Satan himself, sometimes depicted with a displaced eye on his body.
Multiple eyes could also have positive symbolism, representing vigilance and the light of stars in the night sky. The peacock attribute of Amitabha, the Tibetan meditative Buddha of Infinite Light, has this symbolism (through its multi-eyed plumage).
The eyes of some other animals had clairvoyant meaning. Hence the Parsee custom of bringing a dog to a deathbed so that the dying could see the afterworld in its eyes, and the belief of the Aztec shamans that they could read the mysteries of the spirit world in the eyes of the jaguar.