Magic lantern slide c. 1880.
Albert G. Mackey, in his Encyclopaedia of Freemasonry writes two pages on the number seven, claiming : "Seven is a sacred number in Masonic symbolism."1
But the point must be stressed that the number seven is not a "sacred" number in masonic ritual, it is a "significant" number. The sacredness or importance of the number seven in many belief systems, mythologies and cultures is recognized by knowledgeable freemasons but the number itself is not specifically masonic.
Geometry was considered one of the seven noble or liberal arts and sciences, the others being Grammar, Rhetoric, Logic, Arithmetic, Music and Astronomy. In ancient Kemet, or Egypt, the number seven represented completion. Creation took place in seven time periods. There are seven colours in the rainbow, seven notes in a musical scale, seven days in a week, &c.
In Ancient Kemet, there were also seven cardinal principles/virtues of the Goddess Ma'at to achieve human perfectibility. These principles are Truth, Justice, Balance, Order, Compassion, Harmony, and Reciprocity.
In Freemasonry seven brethren are required to open or work a lodge: three Master Masons, two Fellowcraft and two Entered apprentice. While those fascinated by numerology will make much of the two rows of seven tassels found on most Master Mason aprons, this was an aesthetic choice made by regalia makers and has no masonic significance.
The number seven was said to be 'perfect' because it contained the numbers 3 and 4 3 and 4, the triangle and the square, the perfect figures and was itself indivisible and could not be created by multiplication.
Some freemasons will claim that together the seven officers represent how human consciousness works. They represent the co-ordinated parts connecting Man's outer nature with his inmost Divine Principle. They provide the necessary channels for the various spiritual and material levels to maintain contact. This, like much hermetic and sacred teachings, is not fundamental to masonic teachings but should be of interest to all students of Freemasonry.
1. See : phoenixmasonry.org for full text.
Image : Magic lantern slide 18 "The Seven Liberal Arts." c. 1880. Unknown provenance.