It was believed by the ancients that when a soul incarnated, it came down from the "Higher Heavens", through the outermost sphere of the fixed stars, and passing down through the planetary spheres, eventually entered a mother's womb on earth. As it passed through the planetary spheres, so it received a portion of each planet's nature. This would vary in quantity and quality according to the position of the planet in the sky at birth. The agglomeration of this starry or "astral" stuff gave the person being born their character. According to the quantity or deficiency of these gifts of the planets, so would be determined the talents and weaknesses of the incarnating individual. This idea is still, of course, the basis of astrology today, though the philosophy is not usually put in such material terms. It is also the idea behind such fairytales as the Sleeping Beauty, where the fairies (symbolizing the planets) cast spells on the new-born "Beauty"—each in accordance with its own nature.
According to the Hermeticists, after the death of the physical body the soul of an individual would attempt to ascend through the planetary spheres on its way back to its Maker. The spheres represented stages on this journey, rather like rungs on a ladder. As it passed through the domain of each planet it was required to give back to its "governor" the portion of astral stuff it had earlier received on the way down. Thus we read in the Hermetica:
‘At the dissolution of your material body, you first yeield up the material body to be changed, and the visible form you bore is no longer seen. And your vital spirit [literally breath] you yield up to the atmosphere so that it no longer works in you; and the bodily senses go back to their own sources, becoming parts of the universe, and entering into fresh combinations to do other work. And thereupon the man mounts upward through the structure of the heavens. And to the first zone of heaven [Moon] he gives up the fore which works increase and decrease; to the second zone [Mercury], the machinations of evil cunning; to the third zone [Venus], the lust whereby men are deceived; to the fourth zone [Sun], dominating arrogance; to the fifth zone [Mars], unholy daring and rash audacity; to the sixth zone [Jupiter], evil strivings after wealth; to the seventh zone [Saturn], the falsehood which lies in wait to do harm. And thereupon, having been stripped of all that was wrought upon him by the structure of the heavens, he ascends to the eighth sphere, being now possessed of his own proper power. [Hermetica p.52-3].
This in outline is the Hermetic doctrine of the soul's journey after death but there is more. Having traversed the planetary spheres, before the ascending soul could get back to God, it had to pass through the sphere of the fixed stars, known today as the "Celestial Sphere". This represents the "Higher Heaven" and lies beyond the jurisdiction of our local solar system with its governors the sun, moon and planets. To get to this Higher Heaven, which could in any case only be approached if it had successfully passed through the spheres of the Lower, the soul had to find its way to a gate. According to the ancient cosmology there were two of these: one was in the northern hemisphere and the other was in the southern. These "stargates" were positioned at the points in the sky where the ecliptic, the pathway of the sun, crosses the Milky Way. Therefore one of these positions was in Sagittarius, above the sting of Scorpio, and the other was in Gemini, above the outstretched arm or "club" of Orion.
The knowledge of the existence of these "Gates of Heaven" seems to have passed into Christianity. Indeed according to the Bible St Peter was appointed "gate-keeper" of heaven by none other than Jesus himself. It is noteworthy that in statues and pictures Peter is generally shown as holding two keys. These are clearly intended to be the keys to the two different gates.
-Adrian Gilbert