A fetishized sexual object is said to be an object which resembles the usual object or bears some kind of relation to it, but is entirely unsuited to serve the normal sexual aim. In fetishism is seems that some degree of diminution in the urge towards the normal sexual aim is necessary. What usually follows is an over-valuation of the object which invariably extends to everything that is associated with it. Any external or internal factors that hinders or postpones attainment of the normal sexual aim will lend support to the tendency to linger over predatory actions to turn and take new sexual aims in replacement. These are said to be the most common and significant of the perversions.
Sadism is said to be active in nature, while masochism is said to be passive.
Therefore sadism is said to correspond to a component sexual instinct which has become independent and exaggerated. It is through a displacement that sadism is said to usurp the leading position of the sexual instinct. Conversely masochism is described to be the situation in which satisfaction is conditional upon suffering, either physically or mentally, at the hands of the sexual object. Masochism, Freud points out, is nothing more than an extension of sadism turned upon the subject's self, which then takes the place of the sexual object. The most remarkable feature of this perversion, says Freud, is that its active and passive forms are habitually found to occur together in the same individual.