Dream interpretation, also called oneiromancy, is called “the oldest oracle” by Plutarch. This art is almost entirely based on determining which dreams are true and which are false. Homer’s Odyssey comments on this, where Penelope, after receiving what seems to be a prophetic dream, describes the theory:
“Dreams are very curious and unaccountable things, and they do not by any means invariably come true. There are two gates through which these unsubstantial fancies proceed; the one is of horn, and the other ivory. Those that come through the gate of ivory are fatuous, but those from the gate of horn mean something to those that see them.”
- Ivory: These dreams aren’t prophetic, instead being insignificant and meaning nothing. The word “ivory” is a pun in Greek for a word that means “deceive”.
- Horn: These dreams are phophetic. The word “horn” is a pun in Greek for a word that means “come true“
Virgil, who writes in Latin rather than Greek, doesn’t have the same pun in his language. Instead, he justifies these words symbolically: Horn is transparent when cut thinly, while ivory isn’t.
To aid in this determination, lists of dream symbols were recorded in scrolls or books and probably sold as popular guides to divination, just as dream books are now.
- When a person of authority—a God or a parent for example—makes a direct prediction, it is a kind of prophesy.
These are prophetic dreams that come without warning, but sometimes we need an immediate answer to a question. In order to trigger a dream, ancient dreamers engaged in the practice of the incubation of prophetic dreams, called incubatio. Famous examples happen in the temples and sacred shrines to Asklepios and Endovelicus, where the ill come to give an offering, sleep on the skin of the sacrificed animal, and dream of their cure. These cures could be miraculous, medical, or even a mixture of the two (such as requiring that the worshiper take some ashes from the altar and drink them in wine). After receiving the cure, the cured would make a votive offering often in the shape of the organ afflicted. Quite a lot of these votives have turned up in these temples of incubation.
The Stoic Posidonius (135–51 BCE) explained that there are three ways by which dreams can reveal hidden truths:
- First: Since the human soul is divine, being made of the same incorporeal substance as the Gods, it has the same visionary powers as they do, but these powers are obscured and confounded by the soul’s entanglement with the body. The soul, however, is loosened from the body when it sleeps, and thus can see more clearly and recover some of its divine powers. (Which also happens when people are near death or in trance.)
- Second: Our realm is full of Daimons, who as mediates between Gods and mortals can facilitate communication. When the sleeper’s soul is free of the body, it is better able to communicate with the Daimons, who act as messengers of the Gods.
- Third: The Gods, being all-powerful, may speak to us directly, quite simply because they can.
Although this is Posidonius’s explanation of prophetic dreams, it is applicable to other kinds of divination as well. It suggests divination, as a whole, will be far more successful if we do them in a meditative state, focusing inward and away from the material or bodies. Invite the Gods or their assistant Greater Kinds to bring the knowledge you seek through prayer and offerings.
Certain folk traditions of incubation survive, indicating that incubatio may have also been done on a private scale. One could attempt incubating dreams before they sleep with a prayer including a vow of an offering if the dream comes through.
The Greek Magical Papyri provides a large selection of possible methods to achieve incubatio; some simple, some more complex. By large they involve writing a particular incantation or the question on an object which is then slept on or near, or burned as the wick of an oil lamp.
Dervenis, Kostas. Oracle bones divination: the Greek I Ching. Rochester, VT: Destiny Books, 2014.
Dunn, Patrick. The practical art of divine magic: contemporary & ancient techniques of Theurgy. Woodbury, MN: Llewellyn Worldwide, Ltd, 2015.
Opsopaus, John. The oracles of Apollo: practical ancient Greek divination for today. Woodbury: Llewellyn Worldwide, Ltd, 2017.