What is the Thema Mundi?
It’s been said the Thema Mundi represents the birth of the cosmos. Others suggest it’s the birth of our solar system. Another claim is that periodic destructive events occur in the Ages of Cancer or Capricorn or when certain planetary alignments occur in those signs. Some even suggest it’s the birth of God. We disagree. The Thema Mundi is more practical and down-to-Earth than that.
Based on the evidence, we submit it marks the rebirth of humanity after the Deluge (the correct translation of the Sumerian-Akkadian loan-word appearing in Genesis 6 of the Hebrew texts by Hebrew scholars not the silly stupid “flood” in the erroneous King James Version) which the Sumerians say occurred in the Age of Leo and fits perfectly with the Younger Dryas Event.
Cancer is the house of the Moon which is fitting since the nature of Moon is to gather. In all ancient cultures the world over, Moon symbolized rebirth due to the fact that Moon is pale and wan (sickly looking) before it disappears. When it reappears it’s all big, bright and shiny having been re-born again. Perhaps it’s mere coincidence, but the Vinca Culture in the Balkans developed the first writing with the Vinca Script during the Age of Gemini and near the end of that Age comes the development of proto-Sumerian glyphs. The Age of Taurus is when things really take off with the growth of city-states that evolve into kingdoms and empires. Following that was the Age of Aries with more wars than you can count.

We don’t think anyone seriously believes the stars were exactly at 15° in each of the signs. Only a couple of Greek and Latin authors make that claim. For one thing, Mercury is never more than 28° from Sun and Venus never more than 46° away.
Notice how the stars are arrayed in order from Mercury to Saturn (excluding Earth). Although the texts never mention it, some smart people pointed out that in relation to Sun, the stars are in the signs where they make their 1st station before turning retrograde. Jupiter sits at the same degree for about 48 days while Saturn can sit at the same degree for almost 60 days. Mercury being the fastest planet sits for 4 days at the same degree. The symbolism is that after trekking on their journey for a time, the planets literally stop and rest in their “houses.” If you were wondering why those are the “solar signs” or “solar group” now you know.
If you take the stars and “flip” them over to create a mirror image with the Moon as the light (instead of Sun), you have your explanation for the assignment of stars to those houses.

Once again we see the stars arrayed in order based on distance. This is the rationale for assigning houses to each of the 7 stars.
Additionally, the Thema Mundi provides an explanation for the signs of exaltation for the stars:

Rhetorius provides an interesting take on the exaltation of the stars although we’re not sure who he’s quoting:
“Why is it that where Sun is elevated, Saturn is depressed; and where Saturn is elevated, Sun is depressed? We say that it is because Sun is the storehouse of fire and light, and the master of the day; while conversely, Saturn signifying the darkness, is cold. Then, at the place where the light of day is elevated, there the darkness and the night is depressed, and that which is cold is warmed. But at the place where the darkness is elevated, there the light is depressed and the day becomes shorter.
And again, why is it that at the place where Jupiter is elevated, Mars is depressed; and where Mars is elevated, Jupiter depressed? We say that it is because Jupiter is the overseer of the life-breath and abundance, while Mars is the overseer of death. Then, at the place where the life·breath increases, there the bringer of death is depressed; and where death increases, life is depressed.
And again, why is it that at the place where Venus is elevated, Mercury is depressed; and where Mercury is elevated, Venus is depressed? We say that it is because Mercury is the master of arguments, while Venus is the overseer of desire and intercourse. Then, at the place where the intellectual increases, the desire and pleasure of intercourse is depressed. And where desire and pleasure is elevated, the intellectual is depressed.
And again, why is it that at the place where Moon is elevated, there nothing is depressed; and where Moon is depressed, nothing is elevated? We say that it is because Moon is the fortune of all. And he whom fortune elevates, no one may depress; while he whom fortune depresses, no one is able to be elevated.”
One of the things you’ll discover is that there’s no such thing as “detriment” or “fall” and when you unshackle yourself from that stupidity the accuracy of your interpretations will increase.