Society's assumptions about free will and individual responsibility must be drastically revised in the light of scientific discoveries about the brain, argues this fascinating study. Drawing on a wealth of recent developments in neurobiology, genetics and brain imaging, Tancredi, a professor of psychiatry and a lawyer, examines new findings about the neurological structures and processes that underlie reasoning, emotions and decision-making. He applies these discoveries to such traditional moral concerns as violence, sexual infidelity, lying, gluttony and sloth, and even financial fraud and gambling. The striking results of this research, he notes, indicate that hormones, drugs, genetic abnormalities, injuries and traumatic experiences all have profound effects on brain structure and functioning, and hence on moral choices; indeed, some experiments imply that our actions are initiated by the unconscious brain before we are consciously aware of them, raising the possibility that our sense of moral agency is a retrospective ""illusion."" Tancredi supplements his rather dry exposition of the science with case studies from his clinical practice, including lengthy profiles of a sex-addicted patient and of a ""biologically driven"" serial killer, and closes by pondering the possibility and perils of a hypothetical Brave New World-style program of neurological intervention-complete with brain implants-to improve morality. Some will consider Tancredi's talk of the ""empathetic"" female brain and ""systemizing"" male brain and his chalking up of pedophilia to ""an imbalance of the monoamine neurotransmitters"" and homosexuality to ""differences in neurohumeral activity during the prenatal phase"" to be glibly reductionist, but many will find his well-researched overview of the new science of the brain a stimulating addition to the debate about human nature.