Talk about what conditions should be met in barter. First of all, the premise of barter must be the development of social productive forces, producing a large number of social surplus values, such as grain and hides. Secondly, the generation and differences of individual or organizational needs, such as farmers who produce food and craftsmen who produce tools. Third, barter will happen under the condition of mutual recognition. This third rule is also very important. If barter cannot be carried out under the condition of mutual recognition, this behavior will often deteriorate. For example, when the conditions are not mature (backed by strong force), Mongolia will plunder the border of the Ming Dynasty endlessly, and the barter conditions are not mature. But like Wanli's later years, "tribute trade" is very good, because the conditions are ripe and the army is watching. Whoever dares to do something will be punished!
Of course, the above three items are definitely not comprehensive. If we analyze it from the perspective of deep economics and study it from the perspective of law, we will get into trouble. We can write a book, at least as a graduation thesis.