In law, there is a known exception to the assumption that moral culpability lies in either individual character or freely willed acts. The insanity defense—or its corollary, diminished responsibility (a sort of appeal to the fallacy of the single cause)—can be used to argue that the guilty deed was not the product of a guilty mind. In such cases, the legal systems of most Western societies assume that the person is in some way not at fault, because his actions were a consequence of abnormal brain function (implying brain function is a deterministic causal agent of mind and motive).