全天下的人都亲如兄弟。也说“四海皆兄弟”。“四海”即东海、西海、南海、北海。古人认为天圆地方，中国居陆地中间，陆地四周由四海环绕。“四海之内”指当时已知的人类生活空间，犹言“天下”，意指全国或全世界。它昭示了中国人兼济天下的博大胸怀、仁爱友善的人文精神。

All the People Within the Four Seas Are Brothers.

This saying means that all the people in the world are as close as brothers. The Four Seas are the East, West, South, and North seas. The ancient Chinese people believed that the heaven was round and the earth was square, with China in the middle of the earth, which was surrounded on all four sides by the Four Seas. “Within the Four Seas”refers to the world inhabited by humans, which is also called “all under heaven”, referring to the whole country or the whole world. This saying shows the inclusive and broad mind of the Chinese people and their compassion, love and friendship towards other human beings.

引例

君子敬而无失，与人恭而有礼，四海之内，皆兄弟也。（《论语·颜渊》）（君子做事认真而不出差错，待人谦恭而合于礼，那么全天下的人都会亲如兄弟。）

A man of virtue always does things conscientiously without making any mistakes and treats people respectfully and appropriately. Then all within the Four Seas will be his brothers. (The Analects)