by accident是副词短语.修饰动词met

基本解释：偶然地；误；不经意，无意中，意外的。

例句

By decision or by accident, by care or the simple rigour 6 of economy, somebody designed it.

有意识地或偶然地, 经过精心构思或仅是出于简单的经济考虑, 一切总是某一个人设计出来的.