It introduces the basic conditions that an act must meet 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 he states that the general basis of this relationship is two people noticing each other. The relationship starts with one person's excitement, then the other person's excitement. Mutual arousal must precede physical contact, these mutual perceptions establish a normal and natural sexual relationship.