One of the most significant characteristics of Defoe's Moll Flanders is his inclusion of perspective. Moll Flanders is herself, the narrator. She has been through a lot and she writes with tremendous perspective on how the world works and what hazards there are. She writes as an older woman who has lived her life in effort of jumping social classes. She was born in Newgate prison and after many misadventures, prison terms and failed relationships, she ends up being married relatively happily and free from prison.
Moll's perspective in all of this comes from her experiences. She has tremendous knowledge about all of society. She is a lower class citizen and criminal, but she has lived with and even married higher class men. Defoe even includes an episode in which she is conned out of her money by a con-man whom she was trying to con herself. She knows the games of all social classes and what it takes to survive in the world.
For example, in talking about relationships with men, she says:
On the contrary, the Women have ten Thousand times the more Reason to be wary, and backward, by how much the hazard of being betray'd is the greater; and would the Ladies consider this, and act the wary Part, they would discover every Cheat that offer'd; for, in short, the Lives of very few Men now a-Days will bear a Character; and if the ladies do but make a little Enquiry, they will soon be able to distinguish the Men, and deliver themselves.
As illustrated here, Moll speaks from experience. She is one of the women that have seen the "hazard of being betray'd." Defoe's use of this perspective adds verisimilitude to the work as a whole.