A friend is a second self.

朋友是另一个自己。

One of Zeno's sayings is: A friend is a second self.

芝诺有一句名言是：朋友如同第二个自我。

A friend is, as it were, a second self.

朋友就好像第二个自己。

A friend is, as it were, a second self!

对啊！朋友，第二个自我。