among civilized people it was once thought that……

问题描述:

among civilized people it was once thought that……
civilized是过去分词做形容词修饰people
was once thought是一般过去时的被动语态?

对的
among civilized people是介宾短语,做句子状语.
was once thought可以翻作“曾被认作是”,it是形式主语,that以及后面的从句才是真正的主语,英语里面经常会为了避免头重脚轻而这样倒装