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…”  Note that Lilly says that the planet at the very end of the 1st house is still considered to be in the 1st house (the body of the planet is still in the first house) but that its “virtue” or significance is more connected with the meanings of the subsequent house because of its conjunction to that house cusp.

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) and also Ptolemy’s use of Equal Houses where the cusp of the First House is the degree of the Ascendant and the entry or boundary of the 1st House is exactly 5 degrees before the Ascendant.

If I understand this correctly, Lilly differs from Ptolemy because the latter actually redefines the beginning of the house to be 5 degrees before its cusp.  Lilly, on the other hand, is merely saying that a planet in the last 5 degrees of a house (within 5 degrees of the cusp of the next house) will have its significance more closely associated with the house whose cusp it conjoins.  In reading the horary literature, it appears that sometimes astrologers adopt the idea of Ptolemy that the house begins 5 degrees before its cusp and at other times the utilize the idea of Lilly that the planet at the end of a house is strongly connected with the subsequent house because of its conjunction with the cusp of that house.


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 exactly 30 degrees or 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 with the cusp of the 1st House on the eastern horizon. Because of the importance of the Ascendant for the survival of the native, the first house of this system becomes a prototype which is repeated twelve times around the horoscope wheel. Each house is modeled after the 1st and derives its power from 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 and the MC as the cusp of the 10th, they took Ptolemy’s ideas about Equal Houses and applied them to quadrant houses of variable length. This approach is not logical because the significance of 5 degrees for a 30-degree Equal House cannot be the same as for a Quadrant House of much greater or lesser dimensions.

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:

Lilly points houses

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.

Interestingly, both Regiomontanus and Placidus believed that they were applying Ptolemy’s ideas about primary motion and primary directions when they published their methods for dividing the quadrants formed by the Angles into a set of 12 houses. Regiomontanus was mistaken, but Placidus seems to have understood what Ptolemy was proposing. Lilly chose to use Regiomontanus houses, which were in vogue at the time. If Lilly had appreciated the importance of Placidus’ restoration of Ptolemy’s ideas, he may well have chosen to use Placidus houses for his horary practice.

Given that the “5-degree rule” was originally developed only for Equal Houses, a simple way to avoid this problem would be to eliminate this 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 as cusp 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.  A colleague told me that a French horary astrologer, Denis Labouré, has abandoned Lilly’s 5-degree rule entirely and gets good results. I am unfamiliar with his work and would like to know more about it.

My goal here is to try to understand what we are doing in horary rather than just taking certain “rules” on faith. Please leave any comments about this topic below.

Addendum (21 Dec 2017):

Feedback from several readers has helped me to clarify my ideas which may appear a bit muddled in the above text. Here are the main points which I think are valid:

  • Lilly most likely took his “rule” that Houses begin 5 degrees before their cusp from Ptolemy’s discussion of the length of life and his development of an Equal House system in which the cusp of the 1st house is the Ascendant degree and the boundary of the 1st house begins 5 degrees before the Ascendant.
  • The importance of 5 degrees is that it represents the orb of influence surrounding the eastern horizon which symbolizes the life force of the individual.
  • Ptolemy postulated that in this system all house were exactly 30 degrees in size, the cusps of all the houses were multiples of 30 degrees from the Ascendant, the boundaries of the houses began 5 degrees before their cusps, and the importance of the various houses for the life and survival of the native depended on the aspectual relationship of the cusps of the other houses to the Ascendant degree.
  • It is illogical to apply the 5-degree rule without modification to quadrant houses because the 5-degree rules specifically has to do with Equal 30-degree Houses from the Ascendant as cusp of the 1st, whereas quadrant houses are rarely exactly 30 degrees in length.
  • It makes theoretical sense to apply the 5-degree rule in quadrant houses where the cusp of the 1st house is the Ascendant, but it does not make sense to apply this rule to intermediate houses of variable length.
  • To summarize: the Ascendant is the cusp of the 1st house in most systems. The Ascendant is the most powerful point in the chart and in Ptolemy’s system has an orb of influence of 5 degrees in all directions, which is used to define the initial boundary of the 1st house as being 5 degrees before the Ascendant. Given the method used to calculate intermediate houses in quadrant house systems, the equivalent of 5 degrees of the 1st house may be significantly more or less than 5 degrees for the intermediate houses.
  • My plan is to write about this last point in another post.

Here is an example, somewhat dramatic, of the kind of difficulty that can occur with the 5-degree rule. Suppose someone in Finland asked a horary question about marriage. In the following chart Mercury rules the 7th house of marriage. What would the horary astrologer (who uses Placidus houses in this case) consider the house location of Mercury to be in this chart? the 11th house because it is only a couple degrees from the 11th cusp? or the 12th house because Mercury is well withing 5 degrees of the 12th house cusp?  The 11th and 12th houses have very different implications for the state of the marriage.

5 deg rule

Interestingly, if we recast the above chart with Regiomontanus houses, the 12th cusp would be at 11 Sag 56 and Mercury would clearly be a 12th house planet.


About Anthony Louis

Author of books about astrology and tarot, including TAROT PLAIN AND SIMPLE, HORARY ASTROLOGY, and THE ART OF FORECASTING WITH SOLAR RETURNS.
This entry was posted in Astrology, horary and tagged , , , , . Bookmark the permalink.

2 Responses to Does the 5-degree rule in horary make sense?

  1. ayves says:

    I’m digressing, but Lilly’s point system is unfair, I think.

  2. Paris says:

    Dear Anthony: Yours last articles seem very fascinating to me because I was interested in the subject and I wrote something about this too. My provisional solution is based in an excel-table with a proportional orbs system. An alternative method would be to subtract 3m56s per degree to the natal sidereal hour for the purpose of recalculate all the house cusps in the proper system. You can found the table here:
    And for more detail (in Spanish) you can look for “Orbes proporcionales para cúspides de las casas” in my website. Greetings.

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