4/Historical Note

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Historical Note on $4$

The number $4$, as was $8$, was associated by the Pythagoreans with the concept of justice, being evenly balanced: $4 = 2 + 2$, where $2$ is the principle of diversity.

Throughout history, the number $4$ has been regarded with particular significance.

There were originally believed to be $4$ elements out of which everything was formed:

Earth, Air, Fire and Water.

There are $4$ humours:

Sanguine, Melacholic, Choleric and Phlegmatic.

There are $4$ cardinal points of the compass:

North, East, South and West.

There are $4$ seasons of the year:

Spring, Summer, Autumn and Winter.

In the Old Testament, there were $4$ rivers which watered the Garden of Eden:

Pishon, Gihon, the Tigris, and the Euphrates.

In Islam, these rivers are:

Saihan (Syr Darya), Jaihan (Amu Darya), Furat (Euphrates) and Nil (Nile).

In the New Testament, there are $4$ Gospels:

Matthew, Mark, Luke and John.

To bring it all full circle, there are believed to be $4$ fundamental forces of nature:

Gravitation, the Weak Force, the Electromagnetic Force, the Strong Force.

The most aesthetically pleasing musical intervals are those whose frequencies are associated with the ratio of $1 : 4$.

Four strong winds that blow lonely
Seven seas that run high
All those things that don't change come what may
But our good times are all gone
And I'm bound for moving on
I'll look for you if I'm ever back this way
Four Strong Winds by Ian Tyson