Recently a colleague asked a question about “prohibition” in horary, which prompted me to look up Lilly’s definition (CA 110):
“Prohibition is when two Planets that signify the effecting or bringing to conclusion anything demanded, are applying to an Aspect; and before they can come to a true Aspect, another Planet interposes either his body or aspect, to that thereby the matter propounded is hindered or retarded; this is called Prohibition.”
“For example, Mars is in 7 Aries, and Saturn in 12 Aries. Mars signifies the effecting my business when he comes to the body of Saturn, who promises the conclusion. The Sun at the same time is in 6 Aries. Now in regard that the Sun is swifter in motion than Mars, he will overtake Mars and come to conjunction with Saturn before Mars, whereby whatever Mars or Saturn did formerly signify is now prohibited by the Sun, his first impediting Mars and then Saturn, before they can come to a true conjunction.”
We could diagram Lilly’s example as follows:
Sun in 6 Aries —> Mars in 7 Aries ——————> Saturn at 12 Aries,
the Sun in 6 Aries, being faster than Mars, first conjoins Mars in 7 Aries and then advances to conjoin Saturn in 12 Aries, “impediting” both Mars and Saturn in the process and “prohibiting” the eventual conjunction of Mars and Saturn from producing the desired effect.
Sahl gives another example of prohibition (see Dykes, Works of Sahl & Mahsa’allah, 2008, p.25) in which the two significators applying to opposition symbolize the potential perfection of a marriage:
Cancer rises and Capricorn is on the 7th cusp. The querrent (Moon ruling 1st cusp) asks a question about getting married (Saturn ruling 7th cusp).
Moon in 14 Scorpio applies to oppose Saturn in 22 Taurus, BUT Mars is in 17 Taurus and the Moon will oppose Mars before she can oppose Saturn, thus prohibiting the marriage from taking place.
Note that in this example Sahl implies that an unimpeded opposition between the rulers of the 1st and 7th houses would indicate the effectuation of a marriage contract. The following image may capture the symbolism of the opposition aspect perfecting a marriage.
A real-life example might make this clearer. In his Horary Case Book (2012) Christopher Warnock discusses a horary in which a woman asks whether a man she is interested in will marry her. The data for the chart are: Feb 3, 2004 at 10 PM EST in Washington, DC. Here is the chart with Alcabitus houses (Warnock used Regiomontanus).
It is a Mars day during a Sun hour. Libra rising makes Venus the ruler of the querent. Aries on the 7th cusp assigns Mars to the prospective husband. Mars in Taurus occupies the home sign of Venus, which is consistent with the querent’s interest in this man represented by Mars. Venus lies in Pisces, the sign of her exaltation, and occupies the term of Mars. Venus is also in the triplicity of Mars, so there is a mutual attraction.
For there to be a marriage we would expect an applying aspect to be forming between Venus (Asc ruler) and Mars (7th ruler), but none exists. From the point of view of the principal significators, there is a mutual attraction but it is not likely to result in marriage.
Next we could consider the Moon as a co-significator of the querent. Here things look better because the Moon and Mars are within orb of a square aspect, and the Moon receives Mars in the sign of her exaltation. Unfortunately, Mars receives the Moon in the sign of his fall, so he is unlikely to be interested in marrying her.
Nonetheless, let’s assume that the applying square between the Moon (querent) and Mars (7th ruler, potential husband) could result in marriage. Next we need to look for any prohibition. In this case, the Moon will first sextile Venus and then oppose Mercury before it can perfect its square to Mars. In addition, the Moon must leave its current sign Cancer and enter Leo to perfect the square to Mars. Venus and Mercury stand in the way of the Moon bringing a marriage to perfection, so it is unlikely that the querent will end up the the 7th house man as her husband.
There are other factors we could look at in this chart, but they all lead to the same conclusion: no, he will not marry the querent.