Anglo-American law is based on the principle that people are, with few exceptions, capable of rational thought and of controlling their behavior. This is a principle that has troubled many psychologists over the last century, and some have tried to challenge it. The 20th century saw repeated attempts by psychoanalysts to change the criminal law. Although that project failed, we are now seeing neuroscientists make similar efforts. Even if this effort fails, we are likely to continue to see this pattern repeat until a few foundational philosophical principles in psychology are challenged and corrected.