Plato's cosmology and the tropical and sidereal zodiacs

1
I recently came across a very interesting paper which considers a major change in conceptions of the cosmos between late classical (pagan) and later medieval (Latin-dominated and Christian) times, after an interruption during the "Dark Ages" and the early medieval period:
https://www.prometheustrust.co.uk/Plato ... eories.pdf

"Today, the prevailing view regarding Plato’s cosmology looks to
Cornford (1937), who relied on Plato’s Timaeus for his interpretation.
In Plato’s account, the Demiurge fashions two circles that intersect
each other at opposite locations.
‘Next, he sliced this entire compound in two along its length,
joined the two halves together center to center like an X, and
bent them in a circle, attaching each half to itself end to end…’
(Timaeus, 36c tr. Zeyl)1
In the modern explanation, these two cosmic circles stand for the
sidereal (celestial) equator and the Zodiac. Here, the celestial equator
represents the motion of the Same (the fixed stars), while the motion of
the Different is the ecliptic, the path of the classical Planets that travel
along the constellations of the Zodiac. This opinion would be voiced
by Jowett (1892), Bury (1929), Cornford (1937) and more recently by
Vlastos (1975).
But this was not how Plato’s cosmos had been viewed by most people
in antiquity. For centuries, Platonist tradition saw the Milky Way as
the heavenly abode of just souls. At the intersections of the Milky
Way and the Zodiac (path of the Planets) stood the gates of the afterlife
according to Macrobius, who commented on Cicero’s ‘Dream of
Scipio’ which was patterned on Plato’s ‘Vision of Er,’ a chain that
spanned seven hundred years. Plato’s pupil, Heraclides of Pontus,
emulated his master with the vision of Empedotimus that reportedly
pointed to the Milky Way as the ‘Underworld in the Sky.’
Both the modern view and the ancient Platonist viewpoint accept the
path of the Planets (ecliptic/Zodiac) as Plato’s circle of the Different.
Where they disagree is in the interpretation of the other celestial circle [the "circle of the Same"]. The modern view sees it as the celestial equator, while the Platonist tradition saw it as the Milky Way."

Latura's analysis would seem to offer an explanation for a sidereal versus a tropical perspective, which could possibly validate both. In a tropical view, it's easy to find a starting point, using either one of the equinox or solstice points. Siderealists have offered various suggestions, notably a fixed star (e.g. Spica), or an approximate axis between two stars (Fagan: Aldebaran/Antares). But John Addey, in his book "Harmonics in Astrology", while favouring the tropical zodiac, claims that harmonics can and do "work" in a sidereal zodiac, on condition that the start of the harmonic waves be calculated with respect to the intersection of a great circle with the ecliptic. He suggests the galactic equator (equator of the Milky Way) as the best candidate.

Of course, neither the celestial equator (or indeed the terrestrial one) nor the exact galactic equator are visible to the eye, but both can be calculated. Astronomers put the galactic equator currently in the final degree of tropical "Sagittarius" (between about 5 and 7° Sagittarius sidereal, according to the ayanamsas most commonly used) (the other intersection being opposite, of course).

(Another very interesting paper by Latura, more specifically on the evolution of the classical view of the Milky Way: https://www.academia.edu/37997678/Milky ... to_Galileo)

Graham