In the last 15 years three books have been published that are critical of air conditioning (Cooper 1998; Ackermann 2002; Cox 2010). No books (or even articles) in those years have been primarily devoted to a general defense. Such a defense should make the following points. Air conditioners reduce disease and mortality, especially among the ill and aged. They reduce aggressive behavior, including road rage, assaults, and murders. They increase the quality and quantity of nighttime sleep. They improve student and worker productivity by reducing noise and increasing the ability to concentrate. They increase comfort and free choice.