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。

The strong man is strongest when alone.

You put together two people who have not been put together before; and sometimes the world is changed, sometimes not. They may crash and burn, or they may ignite and light up the sky.

这个世界是个美好的地方，值得为之奋斗。