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Quote :Morphology of the Folktale
Just as the characteristics and functions of deities are transferred from one to another, and, finally, are even carried over to Christian saints, the functions of certain tale personages are likewise transferred to other personages. Running ahead, one may say that the number of functions is extremely small, whereas the number of personages is extremely large. This explains the two-fold quality of a tale: its amazing multiformity, picturesqueness, and color, and on the other hand, its no less striking uniformity, its repetition.
Here, Propp flags up a contrast between "personages" and "functions." In simple terms, this is a contrast between the characters in a narrative and the roles that these characters play. Why does a character act in certain way? And what impact does this have on the narrative? Propp says that this second question is totally important: we need, he says, to focus not just on how an author or folktale has depicted a character but also on how this feeds into the narrative.
According to Propp, myths and literature may be chock full of different characters, but if you go beneath the surface, you'll find that these characters aren't as diverse as they may seem, because they're all performing similar function. Think about Maleficent in Sleeping Beauty and Lady Tremaine in Cinderella. Sure, they're sort of different on the surface, but they fill the same role in each story, and in that sense, they're functionally interchangeable.
Propp's whole aim in Morphology of the Folktale is to narrow wonder tales down to their key parts and to find out what they've got in common. By taking this approach, Propp finds that these tales are surprisingly similar and repetitive. It doesn't end there, either: Propp says that this kind of repetition is also common in myths, religions, and in narrative in general.