Introduces the basic conditions that an act must satisfy to be considered a perversion. Sexual acts must be unnatural, a fetish, or unnatural inclinations (Nagel, 1). Nagel goes further to discuss a basic definition of a normal sexual relationship and states that the general basis of that relationship is that two people notice each other. The relationship begins through one person's arousal and then the other person's arousal. Mutual arousal must precede physical contact, these mutual perceptions establish a normal and natural sexual relationship