primary_directions_truth_card_placidian_classic_semi_arc - TheDaniel166/moira GitHub Wiki

Primary Directions Truth Card: Placidian Classic / Semi-Arc

Status

  • doctrinal family: historically attested
  • Moira status: admitted on the current narrow in-mundo surface
  • role in Moira: first admitted branch beyond placidus_mundane

Identity

Placidian classic or semi-arc directions are the broader historical Placidian family in which perfection is determined through semi-arc logic rather than by a single simplified software label.

This family is close to Moira's current method, but should not be assumed to be identical to the present implementation.

Mathematical Basis

Direction Space

  • primarily In Mundo
  • may support zodiacal or hybrid applications depending on source tradition, but the core identity is still semi-arc based

Geometric Basis

  • semi-arcs are fundamental
  • proportional ascensional structure is central
  • house and meridian relations are not decorative outputs but part of the directional geometry

Motion Basis

  • direct motion is the ordinary case
  • converse doctrine exists historically, but is not uniform across authors

Key Basis

  • static keys are historically central
  • Naibod and Ptolemaic keying are especially important

Latitude Basis

  • latitude belongs to the bodily or projected placement being directed
  • this becomes one of the dividing lines between classic Placidian practice and simplified zodiacal reductions

Interpretive Meaning

The interpretive claim of this family is that life unfolds through the completion of temporally scaled arcs grounded in the actual diurnal structure of the natal heavens.

Compared with looser symbolic direction systems, the semi-arc family claims:

  • higher dependence on exact birth time
  • closer relation to concrete life events and bodily worldly circumstance
  • stronger rectificatory value

Historical Standing

  • one of the core early modern and later traditional families
  • central to later debates on primary directions
  • often taken by modern software as one of the baseline reference families

This is one of the clearest candidates for a method truth card because it is:

  • historically central
  • close enough to the current Moira implementation to be tractable
  • distinct enough to require formal separation

Distinguishing Features

Placidian classic / semi-arc differs from other families by:

  • treating semi-arc structure as essential rather than incidental
  • preserving the world-frame logic of primaries
  • resisting collapse into plain zodiacal longitude

It differs from Regiomontanus because:

  • the geometry is not house-circle under-the-pole doctrine

It differs from simple zodiacal directions because:

  • perfection is not defined solely on the ecliptic

Main Ambiguities

1. Naming Drift

Modern software often uses labels like:

  • Placidus
  • Placidus mundane
  • Placidus under the pole
  • Placidian semi-arc

These are not always used consistently.

2. Scope Creep

Many later additions are presented as if they belong natively to the family, when they may be later software expansions.

3. Latitude and Aspect Treatment

Different authors and programs disagree on:

  • whether aspects are directed mundanely or zodiacally
  • whether latitude is retained, suppressed, or assigned

Moira Admission Policy

Moira now admits this family explicitly and separately from current placidus_mundane, with one important limitation:

  • it has its own current narrow in_mundo semi-arc implementation
  • but that implementation is still only the first admitted numeric slice of the broader historical family

Reason:

  • it is the most natural bridge from the current engine to a broader doctrinally stable subsystem
  • the doctrinal identity is now separated and the current admitted numeric slice has begun to diverge

Implementation Consequences

For later widening, Moira should still specify:

  • active relation policy on the current admitted branch:
    • conjunction
    • opposition
  • exact semi-arc equations and invariants
  • which points are admissible as promissors and significators
  • whether aspectual points are allowed
  • how latitude is treated
  • which converse doctrine is admitted

Research Sources

  • Martin Gansten, Primary Directions chapter excerpt: https://astrology.martingansten.com/wp-content/uploads/2020/08/PrimaryDirectionsChapter.pdf
  • Mastro manual: https://mastroapp.com/files/documentation_en.pdf
  • Halloran primary-directions material: https://www.halloran.com/placidus.htm
  • AstroWiki, Primary Direction: https://www.astro.com/astrowiki/en/Primary_Direction