The systems differ in what supplies the element outside the questioner's control (the fall of cards, the marks of geomancy, the images of a dream, a birth date), and in how tightly the interpretation is codified. Some, like geomancy and the I Ching, are highly formal; others, like dream reading, rest on looser traditions of association.
The atlas describes each method's structure, history and interpretive conventions without endorsing or dismissing the claim that it yields knowledge. Several of the symbol sets used in divination, the tarot, the hexagrams, are also treated as symbol systems in their own right under Tarot, Runes & Number.