《淮南子·汜论训》
在这里是正确的，到那里就可能是错误的；在这里是错误的，到那里就不一定是错误的。这就好像斧刀椎凿各有各的用处一样。
此之是，非彼之是也；此之非，非彼之非也；譬若斤斧椎凿之各有所施也。
What is right here may be wrong there; what is wrong here may not necessarily be wrong there. It is like an axe, a chisel, and a chisel each have their own uses.