to think (i.e. to take it to be true that ...) (Usually there is an implication that the notion is mistaken – except when expressing one's own current opinion.)
(after a noun N and before a predicate P) the reason why N P / Example: 我之所以討厭他|我之所以讨厌他[wo3 zhi1 suo3 yi3 tao3 yan4 ta1] "the reason why I dislike him (is ...)"