Do you know of anyone who is obviously insane?
From whence does come insanity?
Answer: From the free decision to disregard the will and laws of God.
"The Lord will strike you with madness and blindness and confusion of heart. And you shall grope at noonday, as a blind man gropes in darkness; you shall not prosper in your ways; you shall be only oppressed and plundered continually, and no one shall save you."
(Deuteronomy 28:28-29)