When it comes to weigh a planet’s strength in horary, we look both at dignities and house positions. William Lilly teaches on p. 33 of his Christian Astrology, that a planet within 5° of a house cusp is to be counted into the following house.
This apparently easy rule raises the question, whether Lilly considers zodiacal movement, also called secondary motion or primary motion.
Zodiacal (secondary) motion is the usual counterclockwise movement from a planet through the signs, in other words, the planetary’s advancement in longitudinal degrees.
Let’s see this in practise. If Mercury is in the 1st house at 20° Gemini and the 2nd house cusp is at 24° Gemini, Mercury is said to be in the 2nd house. Therefore, he loses some strength since he is not angular anymore. When a planet loses strength and moves from an angular house to a succedent or from a succedent into a cadent house, it describes a progressive decay.
However, when it comes to cadent houses and a planet in proximity to an angle, things change. If a planet is in the 3rd house, which is cadent and weak, but close the 4th cusp, it would be judged as particularly strong. There is no increasing growth of strength, like from a cadent to a succedent to an angular house. The change from a cadent to an angular house is huge. It’s like a beggar becoming a millionaire in just one night.
In the example chart above we see that every planet in the 9th house, that is earlier in degrees than the MC, advances and moves toward the 10th house. Mercury at 11° Aquarius is within the 5° orb and is thus considered to be in the 10th house and therefore particularly strong. Saturn, on the contrary is too far away from the 10th house cusp and therefore considered to be in the cadent 9th house. From this perspective, the Sun is moving towards the 11th house, but would be considered in the 11th only when he reaches 7° Pisces.
A planet in a cadent house is usually considered impeded. We can think of a skilled worker who is unemployed: he does not get the chance to put his skills into practice. Angularity, on the other hand, gives the skilled worker the chance to make the best of his talents.
Lilly’s 5° rule, read in this way, makes a planet falling toward an angle, as in the example above, where cadent Mercury falls into the angular 10th house cusp.
However, the 5°orb- rule if read in zodiacal order does not agree with what we see in the sky.
Indeed, in the sky we see a different movement, called primary motion. This is the movement from the planet’s rise at the eastern horizon to its culmination at the MC and finally its setting in the west (DC). With this movement, there is no such thing as falling into an angle. Indeed, with this system, planets can only fall from an angle.
In the example chart above, we see Mars within 5° orb of the AC. If we consider zodiacal motion, Mars is in the 1st house. But primary motion shows us another picture. In that reference system, Mars is rising at the eastern horizon. Hour by hour Mars climbs higher in the sky.
We can also say that the advancing AC which moves counterclockwise, will bring Mars deeper and deeper into the 12th house, before he starts gaining strength, entering the 11th house. Finally, he rises from the ashes to power when he approaches the MC (see charts below).
As soon as Mars has passed the MC, he leaves his position of power. Now he falls from the stake (or angle) into the cadent 9th house: Once the employee has got her promotion (angularity), she will experience a growing dissatisfaction on the job (cadent house), which inclines her toward taking the challenge (succedent house) to achieve a further increase in her position (angularity).
From the perspective of primary motion, a planet can only fall from an angle to an inferior position. He cannot win the lottery. Before becoming a millionaire (angularity), hard work is required (advancing from cadent to succedent to angle). In the example above, once Mars is in the cadent 9th house, he can advance to the succedent 8th house before he finally sets in the 7th house, where he is angular again. Lilly’s rule under the lens of primary motion can only describe a falling from grace (angle-cadent house) to increasing strength (succedent-angular). It describes a cycle of growth.
A 12th house planet close to the 11th house cusp is increasing its power. It makes sense to assign it to the next house. In the same way, a planet that has reached its highest possible position (success) can only decline from that position.
We cannot use both systems, primary and secondary motion, in order to establish, to which house a planet should correctly be assigned. Primary motion describes an increasing growth of power, followed by a downfall, after which a new cycle initiates, while secondary motion describes an increasing loss of power with an unexpected promotion.
Personally, I check with whole sign houses if a planet rather belongs to the cadent or the angular house. I also do have the impression that we neglect more and more what is actually happening in the multidimensional sky, favouring a bi-dimensional piece of paper, where we only see longitudinal degrees.