Abstract: Paul Ewald was a good physicist on X-ray crystallography. The lattice dynamics was a field where Max Born worked all his life. Paul Ewald and Max Born met and became friends in their earlier life，they regarded each other with respect，and appreciated the academic contribution made by each other. When they had different opinions，they could quarrel vehemently，and had nothing to harm to their friendship，because the aim they quarreled about was to find the truth of fact，and had none selfish. This kind of arguments hardly happened between politicians or litterateurs，even average persons. The attitude of scientists to face facts but not against people are worth learning for all the people in modern society.

Key words: Paul Ewald, X-ray crystallography, Max Born