I Ching, Yijing or Zhou Yi
"Oracle of the moon": © 2000 LiSe
What does it mean, 'inner' and 'outer trigram' (popup)
Fire below Heaven: things become visible, it is clear now what kind they are, because Heaven's laws also show. The law that a human looks different than a dog. Similar creatures tend to cling together, because they recognize each other, or a certain soil favors certain plants. But Fire also shows their differemnces, and Heaven makes sure they live the life they are supposed to live. Not underwater when they have lungs, or in the desert with gills.
Ideogram of the hexagram name: the first character, tong (at the top), is a mould for casting adobe bricks, and the resulting brick: equality, unify, to participate in something together, gather, harmony, stability, to agree, collusion, together, preposition, conjunction. The audition of all feudal lords with the emperor was also called Tong. The second character is ren, person.
Tong is 'same', ren is 'people': Similar people.
The 'Great Image' says: Heaven associating with fire: union of people. The noble one classifies the clans and reads the trails of creatures.
Hex.13 is the contrast of 7, which is about a mass of people who are all similar, but are led by the one who is different. In 13 similarity and difference is relative. You are human, like your neighbor, but different being male and female. A mammal like your dog, but different from furry fourfooters.
One meaning of Tong is 'confusion' - because too much similarity, too little contrast, can cause a lack of overview.