How are doppelgängers used in Vertigo?

Doppelgängers have been used in literature throughout history to represent the struggle between vice and virtue within an individual. This is also called Psychomachia. Applying this to Vertigo, there are few doppelgängers representing the vices and virtues of individuals. The main comparison we can make is between Madeline and Judy. Madeline represents the virtuous aspects of Scotties personality, she represents his desire to be a good person and help those in need. We know this as the only reason that Scotty and Madeline met was because of Scottie doing someone else a favour, his desire to help is what let him to Madeline, and Madeline is the manifestation of Scotties virtuous nature. Judy, on the other hand, represents Scotties Vices, his desire to regain his masculinity and to be the dominant. This is shown by the way he tells Judy what to wear, what color her hair should be, and what to do. This is Scotty trying to regain the masculine qualities he lost at the start of the film and at Madelines death. His fear of appearing weak and powerless leads to him to project these insecurities onto Judy, by making her feel weak and powerless, he establishes himself as the dominant and regains masculine qualities.