The myth of Dionysus tells how Zeus, the highest of the gods, slept with a mortal woman, Semele. Because he came to her in his full divinity, instead of one of the lowlier forms he more commonly adopted when he visited mortal women, his power destroyed her, but not before she had conceived Dionysus. Zeus snatched the son who had been made immortal by virtue of the god's unshielded power, and planted him in his own thigh, so Dionysus emerged as a god, even though born of a common mortal. That made him unique both as god and as human, and caused him to be persecuted by both.

Dionysus, also called Bacchus, was a god with many different faces and was to exert great influence over the Athenian mind. He had his origins in Thrace, and his worship spread throughout Greece and beyond. He appears in all sorts of forms, some to fear and some to wonder at. He was the god of wine, wearing a garb of grapes and animal skins, and he was a tree god, a bull god, a god of fertility. His attendants, the satyrs, were half-men, half-animal, devilish, sensual, flaunting their sexuality and given to excess. Dionysus could also be seen surrounded by women, his followers, the Maenads; he could be sexually ambiguous, at times more female than male. Because he was a comparative newcomer to the pantheon of gods on Olympus, he liked to be viewed as severe, awesome and sternly bearded, but his true spirit is associated with vegetation, with all sorts of rites enacted to promote fertility, and with the mysteries of death and rebirth. He was the bringer of madness, anarchic and revolutionary, the god of masquerade and a maker of magic, the master of magical illusion. He could induce his followers to see the world as it was not. His worship, like his image, took many forms often connected with sexual abandon, and more significant, with trance. For Dionysus was also the the god of possession. He was able to reveal himself directly to the individual. His worshippers were possessed by him, submerged in trance.

In its earliest form the worship of Dionysus was what we would now call a cult, whose aim was to achieve ecstasis - the world from which our own word 'ecstasy' is derived. Ecstasis could mean anything from 'being taken out of yourself' to a profound alteration of personality. His worship took the form of an orgy, which means simply a secret rite or an act of devotion; the sexual connotation came later. At midwinter the Maenads, the women who followed the god, left their homes and made for a wooded hillside on Mount Cythaeron in search of a mystical and frenzied communion with nature, to achieve a state of ecstatic possession.