Does the 5-degree rule in horary make sense?

In speaking of the Ascendant, Lilly writes on page 33 of Christian Astrology: “…what Planet you shall find to be in that space, you shall say that he is in the first house; yet if he be within 5 degrees of the Cusp of any house, his virtue shall be assigned to the house whose Cusp he is nearest…”

Lilly does not explain his theoretical justification for this 5-degree rule. Given his reverence for Ptolemy (including his use of Ptolemy’s formula for the Part of Fortune), it seems reasonable to assume that Lilly took his 5-degree rule from Ptolemy’s discussion of prorogatory places in the Tetrabiblos. Ptolemy’s 5-degree rule is based on the theoretical idea of the great strength of the Ascendant (horizon axis).

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This is what Ptolemy had to say, according to two different translators:

“FIRSTLY, those places, only, are to be deemed prorogatory, to which the future assumption of the dominion of prorogation exclusively belongs. These several places are the sign on the angle of the ascendant, from the fifth degree above the horizon, to the twenty-fifth degree below it ; the thirty degrees in dexter sextile thereto, constituting the eleventh house, called the Good Damon; also the thirty degrees in dexter quartile, forming the mid-heaven above the earth; those in dexter trine making the ninth house, called God; and lastly, those in opposition, belonging to the angle of the west.” (Ashmand version)
“In the first place we must consider those places prorogative in which by all means the planet must be that is to receive the lordship of the prorogation; namely, the twelfth part of the zodiac surrounding the horoscope, from 5° above the actual horizon up to the 25° that remains , which is rising in succession to the horizon; the part sextile dexter to these thirty degrees, called the House of the Good Daemon; the part in quartile, the mid‑heaven; the part in trine, called the House of the God; and the part opposite, the Occident.”  (Loeb, Robbins translation)

Ptolemy is discussing natal charts, not horary ones, and he is making the point that before delineating the future life of the native, the astrologer should determine whether the native will even survive beyond infancy. To do this he considers the Ascendant which symbolizes the life force and vitality available to the native. This life force is concentrated at the degree of the Ascendant but is so powerful that it extends 5 degrees above and below the ascending degree or eastern horizon. It’s as if there is an spherical orb of life force whose center is at the Ascendant degree and whose diameter is 10 degrees, which is one-third of a zodiac sign.

The choice of 10 degrees for the diameter of this orb around the Ascendant is not arbitrary. The benefic planets were so labeled because they promoted life. The greater benefic Jupiter is the most life-affirming planet and is associated with the trine aspect in the Thema Mundi of Hellenistic astrology. The trine, of course, is one-third of the entire zodiac. Proportionately then, 10 degrees within a zodiac sign is equivalent to the the size of a trine within the entire zodiac. I believe that this was Ptolemy’s rationale for choosing the 5-degree orb that surrounds the Ascendant degree as the most life-affirming space in the chart.

Notice especially in Robbins’ translation that Ptolemy is taking about spaces whose size is one-twelfth of the entire zodiac. He begins to number these spaces, starting at 5 degrees above the Ascendant. Thus, Ptolemy seems to be creating an Equal House system (modeled after the Hellenistic Whole Sign house system) that begins 5 degrees above the horizon. The first house of this system becomes the prototype which is simply repeated twelve times around the horoscope wheel. Each house is modeled after the 1st, which is theoretically based on the overriding importance of the Ascendant (horizon axis) for the life of the native.

In Hellenistic astrology, which used Whole Sign houses, there is no mention of the significations of a Whole Sign beginning 5 degrees before the cusp of the zodiacal sign. In fact, such an idea would have been considered senseless by Hellenistic astrologers. In other words, the Hellenistic 1st house was the entire sign ascending. A planet was either in that zodiacal sign or it was not.  Proximity to the horizon in the East (where the life-giving Sun rises) had to do with prorogation or length of life, and not with the significations of the 1st house (as a topical place).

Somehow when astrologers began using the Ascendant degree as the cusp of the 1st house, they took Ptolemy’s ideas and applied them to quadrant houses. Ptolemy’s logic certainly applies to the Ascendant which is recognized as an extremely powerful point in the chart. A similar argument could be made for the MC and perhaps the cusps of the other angular houses in a quadrant system, but this argument has its problems because the MC in Ptolemy’s system may or may not lie in the 10th Equal Sign house from the Ascendant which is the main determiner of all the houses in the chart. The idea of a 5-degree rule for the cusp of a cadent house makes little sense because cadent house are regarded as extremely weak.

In fact, traditional horary ranks the houses by their relative strength with the 1st and 10th being the strongest (perhaps deserving a 5-degree rule because the Asc and MC are such strong points) and the 6th and 12th the weakest (perhaps deserving only a 1-degree ruler, or no degrees at all). How could the cusp of a weak cadent house have the same power as the Ascendant and be deserving of the eastern horizon’s 5-degree orb?

Here is what Lilly himself thought of the relative values of strength for each of the houses in his point system:

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It seems to me that Lilly’s application of Ptolemy’s ideas about length of life to the quadrant house system of horary lacks sound theoretical justification and may even be misleading in the interpretation of horary chart, due to the assignment of significators to the wrong houses. Then again, there is the problem of different quadrant house systems producing different cusps, so that the horary astrologer is never quite sure which house a significator near the boundary between houses “really” belongs.

A simple way to avoid this problem would be to eliminate the 5-degree rule and cast horary charts with Whole Sign houses whose boundaries are unambiguous because a planet is either in a zodiacal sign or it is not. An alternative would be to use Ptolemy’s Equal House system from the Ascendant in which each house, patterned after the 1st, is 30 degrees in length and begins exactly 5 degrees before its cusp (which is always an exact multiple of 30 degrees from the Ascendant degree).

Another issue to be considered is the orbs of the planets themselves. Hellenistic astrologers regarding planets within 3 degrees of each other to be corporally united regardless of sign boundaries. From this point of view, there is a theoretical reason to consider any planet within 3 degrees of a house cusp to be joined to that house.

These are just preliminary ideas as I try to make theoretical sense of the 5-degree rule in horary astrology. Please leave any comments about this topic below.