Plato's Complete Year - © Dr Shepherd Simpson

Definition: [Astrological Ages] The time it takes for all the seven planets, known to Classical astrologers, and the stars in the night sky, as seen from Earth, to return to their origin point. This is sometimes confused with the Great Year or 'Platonic' Year, but in reality it would take a much greater period of time, several hundred thousand years, for all these planet's places in the heavens to come back to a particular starting point.

Plato's Complete Year: Plato writes of the Complete Year in Timaeus - the work in which Plato introduces Atlantis. In paragraph 39c-d, he writes:

In this wise and for these reasons were generated Night and Day, which are the revolution of the one and most intelligent circuit; and Month, every time that the Moon having completed her own orbit overtakes the Sun; and Year, as often as the Sun has completed his own orbit. Of the other stars the revolutions have not been discovered by men (save for a few out of the many); wherefore they have no names for them, nor do they compute and compare their relative measurements, so that they are not aware, as a rule, that the “wanderings“ of these bodies, which are hard to calculate and of wondrous complexity, constitute Time. Nevertheless, it is still quite possible to perceive that the complete number of Time fulfils the Complete Year when all the eight circuits, with their relative speeds, finish together and come to a head, when measured by the revolution of the Same and Similarly-moving. In this wise and for these reasons were generated all those stars which turn themselves about as they travel through Heaven, to the end that this Universe might be as similar as possible to the perfect and intelligible Living Creature in respect of its imitation of the Eternal.

Various commentators consider that Plato is referring above to precession and the Movement of the Ages. Indeed you can find footnotes to this effect in various printed and web versions of Timaeus, which generally then refer you on to the quotation on the Perfect Number of the Divine Creature from The Republic.

That this is not the case becomes clearer when the Classical Greek view of the heavens is taken into account. Firstly, the stars Plato is referring to above, the ones which wander, or turn themselves about as they travel through Heaven, are what we now call the planets. Hence, when Plato refers to the eight revolutions he refers to the revolutions of the five planets known at the time, from Mercury through to Saturn, plus the Sun and the Moon [he actually states this earlier in the work in paragraph 38c of Timaeus] and finally, one more rather mysterious-sounding revolution.

Is this last revolution, then something to do with precession? No. The eighth revolution is simply that of the "fixed stars" of the constellations around the Earth: the sight that the Greeks saw each night in the night sky. This is what Plato means by the again rather mysterious sounding revolution of the Same, [see Timaeus paragraph 39b]. In the Greeks' model of the universe, the stars rotated around the Earth on a great Celestial Sphere. They had yet to discover that the Earth was spinning on its axis, and that the revolution of the stars through the night sky is an optical illusion.

Hence Platos' Complete Year refers to when all the seven planets, and the stars in the night sky, as seen from Earth, return to their origin point. How long this might be is very difficult to say, as it all depends on when Plato took their starting point from. This, he doesn't tell us. However, modern astrologers' computer calculations show it would be in the range of several hundreds of thousands of years, not 36 000, nor 25 770 years. However long it is, it has absolutely nothing to do with a Great Year and no connection at all with precession. It has a lot to do with our wish to read into the works of ancient writers concepts that we now possess, and they did not. Sometimes, we really do know more than they did.

Plato's Complete Year [c 360 BC]