你根本不知道他会作何反应。

You never know how he is going to react.

《牛津词典》

你根本不知道将会发生什么事。

You just don't know what's heading our way.

youdao

你根本不知道自己在说什么。

You don't have the faintest idea what you're talking about.

youdao

So, the radical idea here is you might not know what--why you do what you do and this is something we accept for things like visual perception.

由此引出的一个偏激的观点,你根本不知道自己为何要这么去做,这有点像我们获得视觉感知的过程。

耶鲁公开课 - 心理学导论课程节选