• In the 4th century BC, the Greeks believed they needed to teach children wholesome lessons because they believed the earliest ideas children would take in would become "indelibly fixed."
• In the 16th century AD, historians have noted the integration of the worlds of the child and the adult, where children and adults would share the same games and jokes, including indecent jokes that would not be allowed in school libraries or in broadcasting's "safe harbor" period today.
• At one time, public executions were a leading form of family entertainment.

In western bourgeois society in the 19th century, a new view of the child emerged, and educators and social reformers stressed two things, according to Catherine Ross, professor of law at George Washington Law School:

1. the need to prolong children's innocence as long as possible
2. the importance of teaching children Puritan values, such as self denial

"Today, most observers attribute numerous vulnerabilities to children, including inexperience, lack of education, lack of judgment and mature intelligence," Ross wrote. She also stated that a more negative way to view these vulnerabilities is to see children as naive, foolish and irresponsible.

The concept of "harmful" also has changed over time. Examples of what society has deemed harmful over the past 150 years include:

• gambling
• violence
• train stations
• confectionery stores that sell chewing gum with prizes or that run lotteries
• dime novels, classic books and classic plays that might "arouse in young and inexperienced minds lewd and libidinous thoughts"

However, Plato and Aristotle shared a common belief that most contemporary commentators ignore:

If certain portrayals can arouse the urge to imitate life, then to some degree, all portrayals must possess this same capability.

Aristotle went so far as to say that even music can bring about a "release of emotion," but he never clarified what he meant by that statement.

If pornography is treated differently, hopeless confusion would result, according to Kendrick.

Contemporary author Solveig Singleton, director of information studies at the Cato Institute, argued that images can "invoke powerful thoughts, impulses, and feelings in others...(but) there is no reason to view sexual imagery as being any more powerful than any other kind of imagery."