The meaning is: Many things are desirable--wisdom, courage, decisiveness. But if there is no "good will" governing these, if they are governed by evil, they will only make the evil worse.
其意義是：機智、勇敢、果斷等氣質固然是可欲的，但是如果駕御這些氣質的不是一個「善的意志」，而是一個惡人的話，那麼這些氣質只會增益其惡。