One way to confirm whether one’s assessments and opinions are correct is to verify them through observation and comparison. The method of cross- checking and verification was frequently mentioned in the pre-Qin period. Hanfeizi (280?-233 BC) expounded this method in detail. He believed that to determine whether something was correct or not, it was necessary to compare, check, and verify from various perspectives: from heaven, earth, objects, and human beings. In using this method, one should focus on the practical effects of assessments and opinions. Only such assessments and opinions that can be proven to produce real effects through comparison, cross-checking, and verification are correct. To blindly confirm something without cross-checking and verification is foolish.

Right or wrong, it should be determined by whether a name conforms to an entity or matter. Whether one’s opinions are correct or not should be judged by cross-checking and verification. (Hanfeizi)