As a mystical symbol, it was very important to the secret worship of Pythagoreanism. There were four seasons, and the number was also associated with planetary motions and music.[3]


The first four numbers symbolize the musica universalis and the Cosmos as:

(1) Unity (Monad)
(2) Dyad – Power – Limit/Unlimited (peras/apeiron)
(3) Harmony (Triad)
(4) Kosmos (Tetrad).[4]

The four rows add up to ten, which was unity of a higher order (The Dekad).

The Tetractys symbolizes the four classical elements—fire, air, water, and earth.

The Tetractys represented the organization of space:the first row represented zero dimensions (a point); the second row represented one dimension (a line of two points); the third row represented two dimensions (a plane defined by a triangle of three points); the fourth row represented three dimensions (a tetrahedron defined by four points).

Source: Tetractys – Wikipedia