The Book Of Dead Philosophers (critchley, Simon) / quote 14 of 18
Pythagorean numbers and the music of the spheres
Pythagorean doctrines were bound by an oath of secrecy, so we know very little prior to the version of them that appears in Plato. These include a belief in the immortality and transmigration of the soul and the view that the ultimate reality of the universe consists in number. Pythagoreans regarded even numbers as female and odd numbers as male. The number 5 was called ‘marriage’ because it was the product of the first even (2) and odd (3) numbers (the ancient Greeks considered the number 1 a unit and not a proper number, which had to express a multiplicity). Pythagoreans also believed that their master had established the ratios that underlie music. This had huge influence in the notion of musica universalis or music of the spheres, where the entire cosmos was the expression of a musical harmony whose key was given in mathematics.