正因如此用英语怎么说可以表示为 "precisely because of this" 或 "exactly for this reason". 此说法来源于拉丁语 "propter hoc"，意思是 "因此" 或 "正因如此".

一些例句如下：

Precisely because of this, I have decided to resign from my position. (正因如此，我决定辞职。)

The company was forced to declare bankruptcy, exactly for this reason. (公司被迫宣布破产，正因如此。)

She refused to attend the meeting, precisely because of this. (她拒绝参加会议，正因如此。)