7
The sum of the spiritual 3 and the material 4 is 7. In medieval education, students pursued the trivium (grammar, rhetoric, and logic) and the quadrivium (music, arithmetic, geometry, and astronomy), a total of seven subjects, collectively known as the liberal arts. Pythagorean interest in the mathematical patterns in music gives 7 a privileged role, for there are seven distinct notes in the musical scale—corresponding roughly to the white notes on a piano. Counting from 1, the eighth note up the scale is the exceedingly harmonious octave, which is how the name arose.
The number 7 is often considered lucky, and it has a definite mystique, perhaps because it is a prime number—that is, it cannot be obtained by multiplying two smaller numbers together. There are seven days of the week, named after various ancient gods and planets (Sun-day, Moon-day, Tiw’s-day, Woden’s-day, Thor’s-day, Frigg’s-day, Saturn-day). Tiw was a Norse god of war, parallel to Mars in role but to Zeus in etymology, and Frigg was the Old English version of Frea (or Freya), wife of Woden (= Odin).
Shakespeare wrote of the seven ages of man, an idea that goes back much earlier. In China 7 determines the stages of female life: a girl gets her “milk teeth” at seven months, loses them at seven years, reaches puberty at 2 × 7 = 14 years, and reaches menopause at 7 × 7 = 49. The phases of the Moon last approximately seven days, with 4 × 7 = 28 days in a month and also in a female menstrual period. Many cultures recognized seven planets (Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn) in the sense of “wandering bodies,” unlike the “fixed stars,” which retain the same relative position in the night sky. The seven candles of the Jewish menorah that burned in the Tabernacle symbolized the Creation and, according to the English scholar Robert Graves, may be connected to the seven planets of antiquity.
In ancient Egypt there were seven paths to heaven and seven heavenly cows; Osiris led his father through seven halls of the underworld. The seven deadly sins are well-known in Christian tradition. The number 7 was the fundamental number of the Rosicrucians, who used it as an organizational basis for their text Chymische Hochzeit Christiani Rosenkreutz (1459; Alchemical Wedding of Christian Rosycross). The number was also central to the cult of Mithra, which believed the soul rose to paradise through seven planetary spheres. The Christian idea of seven layers of purgatory may be related.
The number 7 features prominently in folk sayings. Breaking a mirror leads to seven years of bad luck. In Iran a cat has seven lives, not the nine of Western myth.
The most common numbers in the Indian Vedas are 3 and 7. Agni, the god of fire, has seven wives, mothers, or sisters and can produce seven flames. The sun god has seven horses to pull his heavenly chariot. In the Rigveda there are seven parts of the world, seven seasons, and seven heavenly fortresses. The cow has 21 = 3 × 7 names.
In the Hippocratic tradition of medicine, 7 rules the illnesses of the body, with painful illnesses lasting 7, 14, or 21 days. In Germany it was believed that pigs would not contract hog cholera if they were treated for seven days with water containing asphodel. In Jewish magic a fever can be cured by taking seven prickles from seven palm trees, seven chips from seven beams, seven nails from seven bridges, seven ashes from seven ovens…terminating in seven hairs from the beard of an old dog.
