If we set aside complicated definitions, geomancy is the art of obtaining answers through the casting of lots.
Once a person formulates a question and seeks an answer, a sequence of random odd and even values is generated, from which sixteen geomantic figures are derived. These figures form a geomantic chart—functionally similar to a horary chart in astrology.
The art of geomancy lies not only in constructing the chart correctly, but also in extracting the answer from it and translating the symbolic language of the figures into clear human speech.
Historically, geomancy is closely related to traditional astrology and is founded upon many of the same principles of correspondence. In horary astrology, the configurations of the planets reflect the condition of things in the world: a person’s fate, the outcome of an event, the progress of an illness, the success of an undertaking, and so forth.
Geomancy, however—despite its close affinity with horary astrology—works not so much through the literal positions of the seven planets of the Chaldean order as through the way their powers and influences manifest within the human being himself.
For this reason, geomancy is not merely a “daughter art” of astrology, as it was sometimes called in the past, but an independent system with its own logic and its own method of obtaining answers.
In astrology, one seeks answers by looking toward the heavens and observing the motion of the planets. In geomancy, by contrast, the individual participates directly in the birth of the answer through his own action: through gesture, movement of the hand, the act of casting the lot itself.
And if astrology shows how that which is above is reflected below, geomancy reveals something different: how the inner state of a person—the deeper layers of the soul and even unconscious processes—may manifest outwardly through the symbols of the geomantic chart.
Why exactly this works is a separate question. Over the centuries, many explanations have been proposed: spiritual cosmology, unconscious processes, symbolic cognition, synchronicity, and others. Yet regardless of explanation, geomancy has endured for centuries for one simple reason: it produces remarkably precise and practically verifiable answers.