The author reviews some of the social and behavioral factors acting on the brain that influence health, illness, and death. Supported with data from several areas of research, his proposal for understanding health and illness provides both the concepts and the mechanisms for studying and explaining mind-body relationships. The brain is the body's first line of defense against illness, and the mind is the emergent functioning of the brain. This mind-body approach incorporates ideas, belief systems, and hopes as well as biochemistry, physiology, and anatomy. Changing thoughts imply a changing brain and thus a changing biology and body. Belief systems provide a baseline for the functioning brain upon which other variables act and have their effects.