When we study the culture of a different time or place, we read their books, view their paintings, hear their music, and so form for ourselves a concept of what that society was like.
But how much material do we need to form an accurate view? Consider the following:
Shakespeare wrote approximately 154 sonnets, give or take. If I've read only one of them, can I make generalizations about them? What if I've read ten? Or twenty? He wrote around thirty-eight plays; if I've studied one of them, is that enough to form an impression of what his plays are like?
Sophocles penned about 123 plays; if I've read only two of them, can I make categorical statements about what the average Sophocles play is?
The statue of the Minoan Snake Goddess, with her eye-catching topless outfit, is much studied. But that is only one single statue, from a culture that made thousands of statues. Can I make generalizations about their statues from only this one? Or make generalizations about their religions, or about the roles which women played in their society?
Think of it this way: imagine yourself studying history 4,000 years from now, and reading about life in a typical North American city in our era. If you were to read only one magazine from this time, and use it to try to form a general idea about our culture, what would happen if that one magazine were Sports Illustrated? Or Vogue? Or Playboy?
Clearly you need several samples, and various samples, to gain a more accurate concept of society.