Thema Mundi

The Thema Mundi ("World Theme", with 'theme' being a word that also means chart) was a mythical horoscope used in Hellenistic astrology that shows the supposed positions of the seven visible planets (including the Sun and Moon) at the beginning of the universe.

The purely symbolic nature of the chart is readily perceived from the impossible positions of Venus and Mercury in it.

The Sun and Moon, the two luminaries, are assigned to the two signs that correspond to the brightest and warmest times of the year in the Northern Hemisphere, Cancer and Leo.

Finally, Saturn is assigned to Capricorn and Aquarius because of the cold and lack of light during this time of the year.

The natures of astrological aspects are determined by the planets' configurations to the luminaries in the Thema Mundi.