What is the function of the variety of narrative perspectives in Mary Shelley's 'Frankenstein'?

The variety of narrative perspectives in 'Frankenstein' are used by Shelley to relativise the interpretation of any particular narrator, and so to provoke the reader to think harder about the characters and their actions. The dominant perspective is that of Victor Frankenstein, who sees himself as the victim of his circumstances, tortured and pursued by his own monstrous creation. However, this is contested by the Creature's own version of events, in which his attacks against Victor were provoked, not only by his cruel abandonment by Victor at his 'birth', but also by his unjust treatment at the hands of almost every human being he encounters. There is more to the novel however than this symbiotic relationship between the Creature and the Creator; for example, the narrative of Safie offers a story of an outsider who is welcomed and taught, which provides a contrast to the relationship between Victor and the Creature. All of this contained within the letters of Robert Walton, the sea captain, which provides a layer of distance from the narratives, thus relativising each perspective, forcing the reader to decide for themselves over the conflict between the two key characters.