Miller maintains that 'doubles may appear to come from the outside as a form of possession, or from the inside, as a form of projection' . Both novels explore this doubleness, between and within characters.
In Jane Eyre, the character of Bertha Mason can be viewed as both an external double and a projected double to Jane herself. Jane is full of vengeful, raging ire, (of which her name is indicative), and can thus find her literal double in Bertha. Her ire first manifests itself in the 'red room' scene of the opening chapter, foreshadowing the aggression which Bertha is to act out later. The 'fiend-like' Jane is threatened with being 'tied down' in 'bonds' (p7) if she will not submit to her oppression, just as Bertha is tied down after her attack on Rochester, her patriarchal oppressor. While Jane is described as 'a mad cat' (p7), the fully-realised madwoman we are told, flew at Mason and 'worried [him] like a tigress.' (p253).
Jane's battle for acceptance within the patriarchal prison in which she lives, however, necessitates a suppression of this anger. It is this stifling of her selfhood which generates the projected double, which will later actually emerge from Jane's psyche into a materialised separate entity - the stereotype of female madness. Bertha becomes the perpetrator of Jane's impulses, acting out the hidden rage which burns fiercely within her.
In Lowood, through the pacifying influences of Helen Burns and Miss Temple, Jane acquires restraint. However, this passivity can only be borrowed, as both women represent a desired selfhood which Jane can never quite reach. As with her cousins, Mary and Diana, Jane's selfhood 'dovetailed' (p423), with them, never quite combining in a true duality. Although Jane wishes to be like the virtuous Miss Temple and the spiritual Helen Burns, she cannot 'comprehend [the] doctrine of endurance' (p61). Instead, she becomes Helen's dark-double in the same way that Bertha is hers, acting out the rage of the oppressed, marginalised, orphan. When Helen is mistreated by the harsh Miss Scatcherd, Jane relates - 'the fury of which she was incapable had been burning in my soul all day.' (p83).
In Thornfield the revenging-double takes on its strongest form. It is during her reverie of longing to transcend the prison of femininity - which is 'too rigid a restraint, too absolute a stagnation' (p128) - and become part of the symbolic male world from which she is excluded, that Jane hears the mad laugh of Bertha. Her only relief from such oppressive thoughts, we are told 'was to walk along the corridor . . . backwards and forwards', just as later she will be confronted with her own external double as she '[runs] backwards and forwards' in her literal prison (p352). Although the patriarchal forces are more subtle at Thornfield, they are far more insidious. For through her intimacy with Rochester Jane suffers the trepidation of a dissolution of selfhood. She says of him fearfully, he is 'an influence that quite mastered me - that took my feelings from my own power and fettered them in his' (p207). As Gilbert and Gubar point out, it is after Rochester's sadistic attempts to gain mastery over Jane's emotions, by making claims of love for Blanche Ingram, that Jane is woken up by the screams in the attic, as Bertha physically attacks Mason. Although Jane doesn't openly rage at Rochester's behaviour, her secret double revolts. This double is both an external and a projected double; and thus the patriarchal house with its imprisoned madwoman is...