- also known as Haylāj, Hylech, Apheta, Alpheta or 'Prorogator of Life'.
The planet or point considered to have the greatest influence upon vitality and so known as "the giver of life". It was used in the calculation of the length of life, and directions or contacts between the hyleg and destructive planets or places (Anareta) were used to mark periods where life was endangered. The strength and fortitude of the ruler of the Hyleg, the Alchocoden, was also considered.
An 'hylegiacal' or 'aphetic' place relates to the houses in which Ptolemy claimed that any planet to be admitted as hyleg must be located. These are (in order of preference): - the 1st, 10th, 11th, 7th or 9th house.
Ptolemy stated that only the Sun, Moon, Ascendant, Midheaven or Part of Fortune could be admitted as hyleg but later astrologers also allowed Venus and Jupiter or a planet that dominated the pre-natal lunation.
William Lilly's method for obtaining the hyleg, (CA., pp.527-529), was:
For more on the derivation and use of the Hyleg, and the method of determination favoured by Alcabitius see Introductory notes to the third book of Dorotheus.
Take either the Sun or Moon if they fall in one of the hylegiacal houses. In diurnal charts prefer the Sun to the Moon (and vice versa) but take essential and accidental dignity into account and remember that a luminary in the first house would be preferred over one in the 9th.
If neither the Sun nor Moon may be accepted as hyleg then:
If the chart is diurnal:
Look at the chart for the New Moon preceding the nativity. See which planet is the almuten of the degree of the New Moon and also consider the planet that has the most essential dignities - if either falls in an hylegiacal house in the nativity it may be accepted as hyleg.
If not, accept the ascendant for the hyleg.
If the chart is nocturnal:
Consider the planet that has most essential dignities in these three places:
The degree of the Moon in the nativity
The place of the luminary (Sun or Moon) found above the earth in the Full Moon preceding the nativity
The place of the Part of Fortune in the nativity
If this planet falls in an hylegiacal house accept it as hyleg.
If not, then use the ascendant if the birth was preceded by a New Moon.
If the birth was preceded by a Full Moon, take the Part of Fortune if it falls in an hylegiacal house; if not, use the ascendant.