By focusing on the lesions in Alzheimer's disease, and regarding them as either critical or irrelevant, researchers may have missed much regarding the origin and pathogenesis of this disease. In this article we consider that the lesions are so obvious not only because they are pathognomonic for Alzheimer's disease, but also because they represent a major departure from normal physiology. We suggest that these myriad pathological changes are homeostatic compensatory mechanisms to aging.