He must have come to know those philosophers through secondary or tertiary sources.

他一定是通过第二手或第三手资料了解那些哲学家的。

I've come to know many friends on the Net.

我在网上结交了很多朋友。

We come to know that ours is not the only culture.

我们开始意识到我们的文化并不是唯一的文化。

How did you come to know it?

你怎么发觉这事的？

When do you come to know her.

你什么时候开始认识她的。