The boundary this atlas now draws around divinatory disciplines, tarot, astrology, palmistry, and the many regional and traditional methods gathered under one heading here, is a comparatively recent one. For most of the history these methods share, reading the sky, the shells or the entrails for guidance was not set apart from the systematic study of the natural world; it was frequently the same scholarly activity pursued for the same institutional patrons. Ancient Mesopotamian celestial divination, the subject of a substantial cuneiform record, treated the observation and recording of planetary and stellar positions as knowledge production serving the state, the same observational discipline that also, over centuries, produced the mathematical astronomy later cultures inherited. Astrology and astronomy were not yet two different pursuits; they were one practice whose outputs served both prediction and calendar keeping.
The separation into a legitimate science on one side and a divinatory art on the other happened gradually and unevenly across different cultures and centuries, driven as much by shifting institutional and religious judgment about which kinds of knowledge counted as reliable as by any change in the methods themselves. What this atlas classifies as divinatory today, tarot, cartomancy, geomancy, cleromancy and astrology among them, is not a natural category the practices themselves declare; it is what remained on one side of a boundary that used to run somewhere else entirely, and in a few cultures still does.