A Look at the Concept of Reception
For example, I have a friend who, before I drew up her chart, I assumed that she had a Leo sun sign, when in fact she had a Scorpio sun sign. However, due to mutual reception with Mars in Leo, she has many Leo-type qualities.
Since many astrologers (myself included) consider the majority of planets to be malific (these are Mars, Saturn, Uranus, Neptune, and Pluto), reception provides a strong counterbalance which allows for such pessimism to be largely abated.
Harsh Aspects ExplainedPtolomy describes a system where alternate signs are masculine and feminine. He then states that the aspects (in this case limited to Conjunction, Sextile, Square, Trine, and Opposition) derive their characteristics either from intrinsic properties or from those involving the genders of their signs. Hence oppositions are considered harsh because they indicate the planets pulling the individual in two different directions while conjunctions are considered harmonious due to the fact that they usually occur in the same sign.
Trines and sextiles occur usually within same-gendered signs and so Ptolomy likened their influence to that of friends. Squares usually occur in opposite-gendered signs, so Ptolomy considered this to be a harsher aspect-- one can consider these more sexual and less friendly.
Reception DefinedPlanets are generally said to rule certain places in the sky. The rulerships can be of the sign, of the triplicity, of the decan (10 degree divisions within the sign), or the Terms (5-day divisions). Also in some signs, the planets are stronger and are said to be exalted. In general, I consider sign rulership receptions to be strongest, then exhaltations, then rulerships of decan, term, or triplicity (in that order). Care must be taken to separate the concept of essential dignity-- that is rulership of a part of the ecliptic with accidental dignity which is defined as rulership of houses. House rulerships do not afford any receptive benefit.
Even a malific planet such as Mars or Saturn which is in its own house is said to act positively due to the requirements of rulership.
So, suppose we have Saturn in Taurus in a square with the Sun in Aquarius. In general, this would be considered a difficult aspect, as the Sun is in its detriment and is afflicted by a harsh aspect from Saturn, the most malific planet known to the ancients. Yet here something interesting happens. Since Saturn rules the sun sign, then it is in a position of ruling the sun, and so the interaction is a benevolant one. The level of protection afforded to both would be much greater if Saturn were in Leo, so each planet ruled the other.
Mutual vs. Nonmutual ReceptionThe first example above was one of non-mutual reception-- i.e. Saturn rules the Sun but the Sun does not rule Saturn. In these cases, the protective nature of reception only extends to the interaction between the two celestial bodies. Also note here that Saturn would be afflicted by the square with the Sun even though the Sun is not afflicted.
If Saturn were in Leo, however, something else occurs. Here the Sun and Saturn rule eachother and they are able to provide assistance to eachother. Mutual reception is not limited to the aspects and can abate all other forms of malice. In essence, in this case, if Saturn were in Leo and the Sun were in Aquarius, the chart could also be read as if Saturn and the Sun switched places and the most beneficial aspects of each reading could be taken. Think of this as a sort of network effect. Mutual reception is therefore limited to a single combination of two planets.
Non-Mutual Reception in a Natal or Synastry ChartNon-mutual reception abates any malice or affliction resulting from the aspect on the receiving planet. Note that in more complex configurations, this may not be sufficient to truly make a hard configuration easier to deal with. For example, in my chart, I have a T-Square involving the Moon and Pluto in Libra, Venus in Aries, and Mars in Cancer. Nonmutual reception includes Venus receiving Mars, Mars receiving the Moon, and the Moon receiving Venus. Therefore Venus is somewhat unaflicted except by the opposition with both the Moon and Pluto. Mars is mostly afflicted by the square with Venus, and the Moon is aflicted by its conjunction with Pluto (in the 8th house, so Pluto is accidently dignified) and its opposition with Venus. However the configuration is far less stressful than it would be if there was no reception.
Non-Mutual Reception in a Horary ChartBecause horary astrology is far more exacting regarding how the planets are used, Non-mutual reception is generally very positive provided that both planets involved are normally used in the horary process. For example, if one asks about borrowing money and the ascendant is in Taurus and the 8th house cusp is in Capricorn, one would first look to the interaction between Venus and Saturn. Saturn is an unfortunate planet, and if it is, say, approaching a square square Venus in this chart, we would read it badly. But if this is the case where Venus is in a sign ruled by Saturn, then we can read the impending square as a positive sign.
Mutual Reception in a Natal or Synastry ChartMutual reception is far more powerful than non-mutual reception. In this case, the celestial bodies actually take on characteristics as if they were in the places of their rulerships. So if you have mutual reception involving the Sun, the individual will have some Leo sun-sign characteristics.
In general, mutual reception abates all malice on either planet involved. This means malific stars have far less influence on planets in mutual reception than they might have otherwise.
In synastry charts, this can indicate a very powerful transformative impact between two people. For example, if one has Saturn in Leo and is working (or in love) with an Aquarius sun-sign type, for the purposes of the joint projects, each person will make the other more complete and stronger (more disciplined, yet more relaxed, etc). Especially when the luminaries are involved, this can be extraordinary.