This problem is one of the major general themes repeatedly expressed by Lawrence B. Erlich in A Textbook of Forensic Addiction Medicine and Psychiatry. Erlich, who is certified in both addiction and forensic psychiatry, emphasizes that the rules of conduct in the legal arena are dissimilar to those in medicine. As an example, he compares the difference between "truth" in the legal sense and the definition of truth embodied in medicine. In law, truth is what is logical, or what "makes sense." However, in medicine something that seems to make sense in reality must be proven through a well-designed study before it can be accepted as truth. Throughout his book, Erlich points out how these differences in the meaning of truth represent limitations of each of these disciplines. He defines the roles of the physician, the attorney, and the court in a forensic psychiatric case.