First, this system is new, I figured it out a couple of years ago.
I think that the nodal axis is a special evolutionary path, related to the Divine.
If you are a Christian, you may correlate it somehow with Jesus' birth of Spirit and Matter, that is of Holy Spirit and of Virgin Mary. Analogically, this is similar with the Moon's Nodes, they represent the intersection of the Sun-Earth rotation plane (spirit) and the Moon-Earth rotation plane (matter).
The nodes represent therefore the reason the spirit incarnates this time, the reason of our current life.
Jesus' life was a symbol for all existence. As a Son of God and as God himself at the same time, this couldn't represent less.
In astrology, we see this symbolism reflected in many ways:
- the 12 apostles = the 12 zodiacal signs, 12 types of human experiences, all leading to the Divinity
- the 4 evangelists that transmitted Jesus' teachings (the 4 gospels represent the basis of the New Testament and of Christianity) - are associated with the 4 fixed signs of the zodiac
- two important events in Jesus life before all biblical events - the visit at the Temple at the age of twelve and the hard test of spiritual maturity - fastening in the desert and overcoming of temptations - are related to the first Jupiter return (occurring at age 12) and the first Saturn return (age 30).
In oriental spirituality, the nodal axis correlates with the subtle energetical channels running through the spine upwards.