IN 1976 in his presidential address before the International Society for Cardiovascular Surgery, Frank Spencer, MD, said, "Deductive reasoning is essential for the surgeon for many reasons, not the least of which is the evolution of operative techniques." In my surgical training at Parkland Memorial Hospital in Dallas, Tex, I saw many examples of deductive reasoning, but 2 experiences during my second year stand out. When I left medical school, I had planned on a career in internal medicine, but after 3 years on active duty in the Air Force, I switched to general surgery and returned to Southwestern Medical School in Dallas. At that time Ben Wilson, MD, was chair of the department, and Tom Shires, MD, was an associate professor of surgery.