The noun form denoting madness, mental derangement, or irrational behavior. Second Peter 2:16 uses it to describe Balaam's madness—his folly in pursuing divination profit contrary to God's will. The term marks behavior so contrary to reason and righteousness that it appears insane. A donkey speaking human language to rebuke a prophet's greed provides scriptural evidence that sin produces a derangement more profound than clinical insanity—moral madness immune to rational argument.