
Hangul concept in Haeryebon book.
Heaven, Earth, Human
At that time, the sources of all things were perceived as heaven, earth, and human. King Sejong believed that the source of all things and the source of sound were not different. Therefore, he thought that letters could be created from circles, squares, and triangles, symbolizing heaven, earth, and human.

The source of all things.

The source of sound.
The concept of “천지인 (Cheon-Ji-In)” translating to “heaven, earth, and human”, the circle represents the round sun (heaven), the square represents the flat earth, and the triangle represents a standing human figure.