Paraphilia (from Greek para = beside and -philia = friendship, meaning love) describes the experience of intense sexual arousal to highly atypical objects, situations, or individuals.
Which practices that have been defined as paraphilia has changed over the course of time and with changes in "religious" control over modern society and so a freedom of moral conscience. A striking example being homosexuality, which was considered a mental illness. The educated and enlightened thinkers of many communities now find such an idea as abhorrent.
What is acceptable sexual practice varies across cultures. This in part is reflected by the age of consent across nationalities; which range from 12 to 21.
Striking disparages showing in the Phillipines where female to male age of consent is 12 and 18 for female to male respectively; but for any male to male or female to female sex is 18. And in Burkina Faso where the age for female to male sex is 13 for both sexes, but for male to male or female to female is 21 for both. Not to mention the places where homosexuality is illegal.
Given this great variation is what is legally acceptable (thereby one would conclude socially acceptable within that culture) and what one place would deem as acceptable another would deem as aberrant.
How can paraphilia be, scientifically, defined on behaviour alone?
Are there neurobiological differences between the brain of a "paraphilic" and a "normal"?
What is the correlation between other mental illness and/or abnormal psychology and paraphilia?
note: this lends itself to what we define as illness or abnormal psychology