LUNACY

[noun] [U] - wild foolishness or dangerously unsuitable behaviour which is against reasonIt would be lunacy to try and climb the mountain in this weather."She said she was going to try and get him to change his mind." "But that's lunacy!"It was sheer lunacy for him to think they would agree to his proposals.It's the sheer lunacy of his comedy that appeals to such a wide range of people.(dated, now taboo) Lunacy is also mental illness.