以物易物、互通有无的倾向是人类共有的，也是其他动物所没有的。
Positive emotions broaden our awareness and encourage novel, varied, and exploratory thoughts and actions. Over time, this broadened behavioral repertoire builds skills and resources.
The strength of a political system lies in its ability to adapt to changing circumstances and to incorporate new ideas and practices.
Live truth instead of professing it.