madness

The king's madness [=insanity] was well-known.国王的疯病众人皆知。

He suffered a series of tragedies that nearly drove him to madness.他遭受的一系列悲剧几乎令他精神崩溃。

Her friends told her the idea was pure/sheer madness, but she went through with it anyway.朋友们告诉她那想法简直是愚蠢至极，但是她就是执迷不悟，坚持付诸实践。

It was the height of madness for him to drive at such high speeds!车开得那么快，他简直是够疯的！