Mr. Wang Li's "Ancient Chinese" also used this sentence: "There are friends in ancient times, but today is different. Classmates (teachers) are friends and comrades are friends. " Take the word "friend" as an example. The ancients valued "different ways, no common cause, no common goal" and hoped that like-minded people would discuss the problem together. There is a poem in The Book of Songs Xiaoya Logging, which means that people need like-minded people to promote each other.
There is a similar saying in the Book of Rites: "He who studies alone without friends is ignorant." Obviously, "friends" here all refer to "like-minded people" and can't be replaced by "friends". Like-minded friends can easily vote for the same teacher and become friends, while friends of the same teacher may be influenced by their own teachers and become like-minded friends, so it is difficult to distinguish between friends and friends in the future, thus forming a stable structure like friends.