I have learned the most important language by meeting a wide range of people from different cultures.
我接触到许多来自不同文化的人,掌握了最重要的语言。
Kill two birds with one stone.
一举两得。
Even if one didn't know from concrete examples (the 1936 Olympic Games, for instance) that international sporting contests lead to orgies of hatred, one could deduce if from general principles.