Arabic Parts & Lots (阿拉伯點與希臘化配分)

The Lots — Fortune, Spirit and the Sensitive Points of Traditional Astrology

Overview

The Lots — better known in the medieval West as the Arabic Parts — are calculated points in a chart, each carrying a specific topic of life. A Lot is found by measuring the arc between two chart factors and projecting it from the Ascendant: Lot = Ascendant + (A − B). The most famous is the Lot of Fortune, but the tradition holds dozens, from the seven Hermetic Lots of the Greeks to the medieval parts of Marriage, Children, Substance and the rest. This endpoint casts the full traditional set from a birth chart, honouring the day/night sect rule that most Lots reverse by.

Origin & history

The Lots (κλῆροι, klēroi, 'allotments') are among the oldest techniques of Hellenistic astrology, described by Dorotheus, Valens and Paulus Alexandrinus in the first centuries CE. The Greeks worked with a small, coherent set — pre-eminently the seven 'Hermetic' Lots attributed to Hermes Trismegistus: Fortune and Spirit (the lunar and solar lots) and the five derived from them — Eros, Necessity, Courage, Victory and Nemesis. As the tradition passed to the Persian and Arabic astrologers (Māshāʾallāh, Abū Maʿshar, al-Bīrūnī) the technique multiplied into hundreds of 'parts', one for nearly every conceivable topic, which is why the Latin Middle Ages knew them as the Partes Arabum, the Arabic Parts.

The pivotal question in the whole subject is SECT. Vettius Valens and the Hellenistic tradition compute the Lot of Fortune one way by day (Ascendant + Moon − Sun) and the reverse by night (Ascendant + Sun − Moon) — and likewise reverse Spirit and all the derived lots. Ptolemy, by contrast, computes Fortune the same way regardless of sect, and much of modern Western astrology follows him. The two schools can place Fortune in different signs. This engine follows the traditional sect-reversed convention (Valens), and discloses the Ptolemaic non-reversed alternative. The medieval Arabic parts inherited the same logic unevenly — some reverse by sect, some by gender, some not at all — and their formulae genuinely diverge across al-Bīrūnī, Bonatti and Lilly; the engine implements the dominant form and names the divergence on each affected part.

How it works

From birth date, time and place, the engine computes the Ascendant and the seven classical planets on the tropical zodiac with its Meeus-precision ephemeris, and determines sect rigorously from the Sun's altitude — above the horizon is a day chart, below is night. It casts the two luminous lots first, Fortune (Asc + Moon − Sun by day, reversed by night) and Spirit, then the five derived Hermetic Lots — Eros (from Spirit and Venus), Necessity (Fortune and Mercury), Courage (Fortune and Mars), Victory (Jupiter and Spirit), Nemesis (Fortune and Saturn) — each built from the already-sect-reversed base, so a night chart carries two independent reversals. It then casts the medieval Arabic parts (Marriage, Children, Father, Mother, Siblings, Sickness, Enemies, Real Estate, Faith, Friends, the 8th-place, Substance), marking whether each reverses by sect, uses a house cusp, or diverges across sources. Every Lot returns its degree, sign, whole-sign house and formula.

Good for

Use cases

Fortune & Spirit

The two luminous lots — Fortune (body, livelihood, circumstance) and Spirit (mind, action, career) — cast in their correct sect-reversed form for your chart.

The Hermetic Seven

Eros, Necessity, Courage, Victory and Nemesis, each derived from Fortune or Spirit — the coherent Greek set with their classical meanings.

The Parts of Life

The medieval parts for family and circumstance — Marriage, Children, Father, Mother, Siblings, Substance and more, each with its formula and the sources' divergences flagged.

Sect Done Right

Sect is determined from the Sun's actual altitude, and the Lots reverse accordingly (Valens); the Ptolemaic non-reversed Fortune is disclosed as the alternative.

Key terms

Lot / Part
A calculated point, Ascendant + (A − B), carrying a topic of life — the Greek klēros, the medieval Latin pars.
Lot of Fortune (Tyche)
The lunar lot of body, health and material circumstance — Asc + Moon − Sun by day, reversed by night.
Lot of Spirit (Daimon)
The solar lot of mind, will and action — Asc + Sun − Moon by day, reversed by night.
Sect
Whether the chart is diurnal (Sun above the horizon) or nocturnal — the condition that reverses most Lots' two terms.
The Hermetic Lots
The seven-lot set attributed to Hermes: Fortune, Spirit, Eros, Necessity, Courage, Victory and Nemesis, the last five derived from the first two.

API

The askTIAN Arabic Parts & Lots endpoint casts the traditional Lots from a birth chart. It computes the Ascendant and seven classical planets on the shared Meeus ephemeris, determines sect from the Sun's altitude, and returns the seven Hermetic Lots (Fortune, Spirit, Eros, Necessity, Courage, Victory, Nemesis) plus the medieval Arabic Parts (Marriage, Children, Father, Mother, Siblings, Sickness, Enemies, Real Estate, Faith, Friends, the 8th-place, Substance) — each with its degree, sign, whole-sign house, formula, sect-reversal flag, and a disclosed divergence where sources disagree. It follows the traditional sect-reversed (Valens) convention for Fortune and discloses the Ptolemaic alternative. Gold-locked to a hand-computed synthetic chart in both sects. A best-effort LLM reading is returned in parsable sections (set interpretation:false for structured data only). Honest rails: exact arithmetic, a symbolic reflective technique — the Lot of Death marks the 8th-place topic, not death-timing; no lifespan, no medical/financial/legal advice.

Endpoint: POST /trpc/lots.calculate — 3 TIAN Points. See the API documentation and Playground.