HOUSE SYSTEM · Geç Antik / Late Antiquity

Porphyry

Porphyry of Tyre (~234-305 CE)

quadrant origin · equal trisection · mathematically simple · Hellenistic middle way

How it divides the sky

The simplest quadrant system. Divides each quadrant (Asc-IC, IC-Desc, Desc-MC, MC-Asc) into three equal arcs. So the arc from Ascendant to lower meridian is divided into 3: houses 1, 2, 3. Other quadrants the same. Yields very similar results to Placidus at mid-latitudes; the math is simple.

When to use it

If you want quadrant-based houses (Asc + MC tied to house cusps) but want to avoid Placidus's complexity, choose Porphyry. Some Hellenistic astrologers prefer Porphyry over Whole Sign.

History

Late Antique philosopher Porphyry published it; actually appears in earlier Hellenistic sources. The name stuck with Porphyry.