Sometimes the ass is representative of sacred, lowly energy necessary to carry the god. In the Christian myth, Jesus appears on Palm Sunday riding a donkey, and Mary rides on a donkey to the stable where she gives birth to Jesus among the animals. The donkey, one of the lowliest of animals, is also, paradoxically, the perfect carrier for birth of the divine. The sensual, lowly instincts in the soul are necessary for birth amid the truly human domains of life, as lowly as the manger scene itself.
Genuine spirit of the ordinary is seen in the ass. The ass brings alive the mediating between human and divine precisely because it brings the ordinary or modest into view. When the modest or ordinary is present, then by contrast the opposite, the divine, constellates. You cannot have one without the other, and if the ordinary is abandoned, then inflation results, and no true union between human and divine can occur. In fact, the presence of the ass also plays with the manifestations of the ordinary and of the divine not as opposites. This leads us to the flame of the Greek goddess of modest, Hestia, whose sacred animal was the ass.
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Psychologically Hestia represents the value of the inner flame of awareness, the warmth of inner being, and the virginal qualities required individuation--remaining true to oneself. She also lights the hearth flame in home life, and is the warmth that gathers people together, an eros flame of community life. Her presence in relationships helps bring humanity alive, and stands in great contrast to the false self constellations which can keep people from experiencing their humanity and true exchanges in a spirit of love.
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When the ass appears in dreams, looking into the particular essence of the appearance of the ass helps reveal the message and meaning. Is the lowly ass drawing you toward genuine modest ground of being where the divine is born, through its Byzantine eyes? Is the bawdy jackass revealing the backside of things by ushering in contact with shadow and a freeing of energy? Is the god Mercurius revealing his royal tricky presence? The nature of the ass is complex, and so the specific details and felt experience of the manifestation is of utmost importance to understand what side of the ass is communicating to you.
from Pregnant Darkness: Alchemy and the Rebirth of Consciousness by Monika Wikman