William Osler's description of the ideal physician remains the dominant character-ideal for modern physicians. He believed that the personality traits that resulted from a belief in ascetic Protestantism, what has been called the Puritan temper, were essential in the practice of medicine. However, this idealism has been weakened by modern psychological theories which view idealism as an illness. In a culture oriented to health, rather than virtue, as an ultimate ideal, physicians can help develop a science of limits.