Yin

Taurus, Cancer, Virgo, Scorpio, Capricorn and Pisces are the six signs of the receptive charge, and they are exactly the earth and water signs. The division is the mechanical alternation from Aries described under the opposite entry: every second sign belongs to this group.

Ptolemy's term is feminine, and the qualities associated with it in the classical scheme are nocturnal, cold, and moist or heavy. The tradition reads the group for gathering, containing and receiving rather than for projecting, and at the technical level it treats the two charges as complementary rather than as ranked. The rhetoric around them is another matter, and the sources do not always keep the technical and the evaluative apart.

Structurally the property is inseparable from the elements. Earth and water are the two heavy elements in the classical physics, the ones that fall rather than rise, and the polarity of the signs restates that at the level of the zodiac. Which is why the charge cannot be used as an independent variable in a reading: knowing that a sign is of the receptive group tells you it is earth or water, and knowing that it is earth or water tells you its charge.

The doctrine of sect applies the same underlying distinction to the planets, giving the Moon, Venus and Mars to the night, and in traditional judgement it is the sect assignment rather than the sign charge that does most of the work.

Sources TetrabiblosClaudius Ptolemy with Hellenistic Astrology: The Study of Fate and FortuneChris Brennan

This entry and its opposite serve two different bodies of material in the atlas, and the join between them is a decision of the atlas rather than a claim made by either tradition.

The first is the Greek alternation of the signs described above. The second is Chinese. Yin and yang are a fundamental pair in Chinese cosmology, and they run through the Yijing, where the broken and unbroken lines of the trigrams and hexagrams are the yin and yang lines, through the ten heavenly stems, which alternate between the two, through medicine, and through the sexagenary calendar. The atlas holds all of that material under its own entries, and several of those tables carry a polarity value that resolves to this one.

Treating one table as serving both is efficient and it is a risk. The Greek property is a mechanical alternation of twelve signs derived from the elements. The Chinese pair is a general principle of complementary opposition applied across an entire cosmology, and it is not derived from anything more basic. They are not the same kind of thing, and a reader should not conclude from a shared label that a Greek feminine sign and a yin heavenly stem are two instances of one category.

So the atlas records the shared label, records that it is a modern convenience, and describes each tradition in its own terms elsewhere. Where a correspondence between the two has actually been proposed by somebody, it belongs under that proposal with its source attached, and not in the structure of a lookup table.

Sources TetrabiblosClaudius Ptolemy with A History of Western AstrologyNicholas Campion