Arabic Parts
AR-uh-bik pahts
arabic: السهم (Al-Sahm)
Definition
Arabic Parts are calculated points on the zodiac — sometimes called Lots. You find one by measuring the arc between two factors in the chart (usually two planets, sometimes a planet and a lot, or the pre-natal syzygy — the New or Full Moon just before birth) and then projecting that same arc out from a third point, most often the Ascendant, until it lands on a single sensitive degree. The general formula is Point = A + B − C, and for many Parts the A and B swap places depending on whether the birth was by day or by night.
In Tradition
In Arabic-Persian and Hellenistic practice the Parts (Greek klēroi, Arabic sihām, Latin partes) are read as derived indicators: each one gathers the meanings of its base points onto a single degree, which is then interpreted by its sign, its house, the aspects to it, and the planet that rules its sign. Abu Ma'shar organises them into seven planetary lots, eighty lots tied to the twelve houses, and ten further lots — ninety-seven in all.
In Practice
You pick a Part for the topic you want, take its particular formula — for the Part of Fortune, Ascendant + Moon − Sun by day, Ascendant + Sun − Moon by night — and project the resulting arc from the reference point in the direction of the signs. The degree you land on is then treated like any other sensitive point: its sign, its house, and its sign-ruler carry topic-specific meaning, and aspects to it, especially from its own ruler, are weighed. Al-Biruni's Tafhim catalogues the three internal reference points of every lot — the beginning (manqūd), the end (manqūd minhu), and the casting-off point (muzād ʿalayhi). When several Parts land on the same degree, that was read as strong confirmation.
Historical Origin
Ptolemy's Tetrabiblos treats only the Lot of Fortune, but the wider lot-system is attested in Dorotheus, Valens, and the Hermes Panaretos that Abu Ma'shar names as his default source. Abu Ma'shar's Great Introduction (9th c., Part VIII) and Al-Biruni's Tafhim §§475-480 (c. 1029) set the corpus in order, and it passed through Sahl, Masha'allah, and Bonatti's Liber Astronomiae (c. 1277) into medieval Latin practice. Holden notes that the modern name "Arabic Parts" is a misnomer — the Arabs inherited most of these lots from the Greeks.
Further Reading
- Al-Biruni, The Book of Instruction in the Elements of the Art of Astrology (Tafhim)
- Abu Ma'shar, The Great Introduction to Astrology
- Benjamin N. Dykes, Works of Sahl & Masha'allah