Research into the brain is changing our view of what it is to be a human being. Our knowledge of core human faculties such as language, social reasoning, aesthetics, and economics is challenged by this research, yielding multiple hard questions. Do we have a free will? Is the mind innate or plastic? Should we surgically or pharmacologically enhance our mental faculties? Can responsibility for crime be determined in a brain scanner? Are our old notions of "human nature" a thing of the past?