How are doppelgängers used in Vertigo?

Doppelgängers are used throughout this film through vice and virtue using different characters for example Madeline and Judy. Madeline brings out the virtue in Scottie as he see's an opportunity given by Gavin to save a vulnerable woman so he can re-gain his masculine qualities as well as wanting to do the right thing and help out an old friend.

When Scottie fails to save Madeline and is unable to be cured from his suffering vertigo he finds Judy - who represents Madeline's doppelgänger. When we see Judy from Scotties POV shots the first shot of her we see is a side on profile shot which is the same shot we first seen Madeline in from his POV. However, this time with judy the shot is not as angelic and desirable as before but more sinister. Scottie see's Judy as a personal desire as she looks just like Madeline - the woman who he fell in love with - and so he gives into his base desires and vices. Judy is just a vice to Scottie as she represents the apparition or double of Madeline which scotties see's as a second chance to help him get over his misfortune and mental illness.

As the film progresses we see a change in Scottie as he becomes ore dominant and demanding with Judy controlling what clothes she wears, her hair colour and overall appearance ultimately to turn her into Madeline. This supports Freud's idea that the arrival of a double or doppelgänger represents the return of the repressed - in Scotties case the arrival of Judy is a way for him to return Madeline who up to this point in the film Scottie still thinks is dead because of him and his vertigo.

This supports the idea that Scottie also suffers from psychomachia - a conflict within the soul. This is used to represent the struggle Scottie is facing with vice and virtue showing the audience Scotties two different personalities toward different people (Judy and Madeline).