# 4/Historical Note

## 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:

There are $4$ humours:

**Sanguine**,**Melacholic**,**Choleric**and**Phlegmatic**.

There are $4$ cardinal points of the compass:

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*

## Sources

- 1980: David M. Burton:
*Elementary Number Theory*(revised ed.) ... (previous) ... (next): Chapter $1$: Some Preliminary Considerations: $1.3$ Early Number Theory - 1986: David Wells:
*Curious and Interesting Numbers*... (previous) ... (next): $4$ - 1992: George F. Simmons:
*Calculus Gems*... (previous) ... (next): Chapter $\text {A}.2$: Pythagoras (ca. $\text {580}$ – $\text {500}$ B.C.) - 1997: David Wells:
*Curious and Interesting Numbers*(2nd ed.) ... (previous) ... (next): $4$ - 2008: Ian Stewart:
*Taming the Infinite*... (previous) ... (next): Chapter $2$: The Logic of Shape: Pythagoras