在英语中，the sheep and the goats常用来意指好人和坏人，因此not tell the sheep from the goats 也就有了分不清好人和坏人的意思了。

如：She can't tell the sheep from the goats. I once helped her a lot, but in the end she said she didn't need my help at all.
       她分不清好赖人。我曾经帮过她大忙，但是最后她竟然说她根本不需要我的帮忙。