It is common for individuals who have not read Shelley's novel to think that Frankenstein is the name of the monster rather than the scientist who created him. However, a careful reading of the novel suggests that this common mistaken in identification has some symbolic truth to it. Certainly Frankenstein and the creature have much in common and could even be two parts of a divided self.
The idea of the double comes from German folklore and is known as the doppelganger or double goer. This is an ancient belief that each living creature has an exact double who exists as a spirit or ghost. There have been many horror and ghost stories that have been written about the idea of a doppelganger.
This idea of duality not only finds its roots in western culture, but also in eastern culture as yin yang.
Watch presentation about Yin Yang in Mary Shelley's Frankenstein.