Literary motif
The Gothic double is a literary motif which refers to the divided personality of a character. Closely linked to the Doppelgänger, which first appeared in the 1796 novel "Siebenkäs" by Johann Paul Richter, the double figure emerged in Gothic literature in the late 18th century due to a resurgence of interest in mythology and folklore which explored notions of duality, such as the fetch in Irish folklore which is a double figure of a family member, often signifying an impending death.
A major shift in Gothic literature occurred in the late 18th and early 19th centuries, where evil was no longer within a physical location such as a haunted castle, but expanded to inhabit the mind of characters, often referred to as "the haunted individual." Examples of the Gothic double motif in 19th-century texts include Charlotte Brontë's novel "Jane Eyre" (1847) and Charlotte Perkins Gilman's short story "The Yellow Wallpaper" (1892), which use the motif to reflect on gender inequalites in the Victorian era, and famously, Robert Louis Stevenson's novella "Strange Case of Dr Jekyll and Mr Hyde" (1886).
In the early 20th century, the Gothic double motif was featured in new mediums such as film to explore the emerging fear of technology replacing humanity. A notable example of this is the evil mechanical double depicted in the German expressionist film "Metropolis" by Fritz Lang (1927). Texts in this period also appropriate the Gothic double motif present in earlier literature, such as Daphne du Maurier's Gothic romance novel "Rebecca" (1938), which appropriates the doubling in "Jane Eyre". In the 21st century, the Gothic double motif has further been featured in horror and psychological thriller films such as Darren Aronofsky's "Black Swan" (2010) and Jordan Peele's "Us" (2019). In addition, the Gothic double motif has been used in 21st century Anthropocene literature, such as Jeff VanderMeer's "Annihilation" (2014).
Origins.
The emergence of the Gothic novel in the 18th century coincided with a renewed interest in Celtic folklore and pagan mythology, which is abundant with supernatural double figures. The period from 1750 to 1830 is known as the “Gothic and Celtic revival” in which the Irish, Scottish, and Welsh folklore which had previously become absorbed into British literature as a result of colonial expansion into these territories began to influence the development of the Gothic genre. For example, the doppelgänger motif was inspired by the Celtic double figure called the fetch or "Macasamhail", a lookalike of a relative or friend who would appear as an omen of death if encountered at night, according to Irish and Scottish superstition.
Short stories detailing encounters with fetches began to appear in the early 19th century, such as the tale "The Fetches" (1825) published by Irish brothers John Banim and Michael Banim, and the collection of ghost-sightings "The Night Side of Nature" (1848) published by Catherine Crowe. Crowe's collection of tales featured a chapter detailing encounters with double figures, including John Donne's claim that he saw a double of his wife holding a dead child in Paris at the same moment she gave birth to their stillborn child in London. In these early Gothic tales, the double was believed to be a sentient spirit which had the ability to leave the physical body and travel to communicate with family members.
18th century.
"Siebenkas" (1796).
The German Romantic novel "Siebenkas" features the first appearance of the term doppelgänger, meaning double-walker. A footnote in the novel which first coins the term defines doppelgänger as “the name for people who see themselves.” Unlike the supernatural fetch in Celtic folklore, in "Siebenkas" the doppelgänger is initially not a supernatural apparition or hallucination but Siebankas’ friend Leibgeber who looks very similar to Siebenkas except for his limp. However, later in the novel the term doppelgänger begins to take on the meaning of a hallucination when Leibgeber is represented as Siebenkas’ alter ego or spectre rather than just his lookalike friend. This novel marked the beginning of the Gothic double motif as a sinister split personality.
19th century.
Victorian Gothic literature altered depictions of evil to explore the potential darkness of the human mind. Rather than evil being an external force such as a ghost haunting a castle, as apparent in early Gothic texts such as Horace Walpole's "The Castle of Otranto" (1764), Victorian Gothic literature examined how evil can exist within the minds of individuals. As a result, the double motif was heavily featured in Victorian Horror to explore the innate darkness of humanity rather than just the presence of external sources of evil. Manifestations of the double motif in this period include mirrors, shadows, reflections, and automatons.
Novels.
"Jane Eyre" (1847).
Charlotte Brontë's novel "Jane Eyre" uses the Gothic double motif to mirror the protagonist Jane Eyre with Mr Rochester's wife Bertha Mason who is imprisoned in the attic of Thornfield Hall due to an unidentified mental illness. This doubling between the identities of Jane and Bertha is used to challenge the expected roles of women regarding marriage and sexuality in the Victorian era. In the novel, Bronte alters the typical use of the double figure by placing the motif into a domestic rather than supernatural context which addresses marriage issues, as Jane is the second wife of Mr Rochester who replaces his first wife, Bertha Mason. While Jane is initially represented as Bertha's replacement and therefore her opposite, their identities are doubled in the novel to represent the powerlessness of women during this era, as both characters are imprisoned within gender stereotypes imposed on them by Mr Rochester. Bertha symbolises Jane's repressed desires for freedom and independence in a context which restricts women's lives through marriage, as evident in the chapter describing the night before Jane's wedding where Bertha appears in her bedroom and rips her wedding veil, as shown in the quote below."“But presently she took my veil from its place; she held it up, gazed at it long, and then she threw it over her own head, and turned to the mirror. At that moment I saw the reflection of the visage and features quite distinctly in the dark oblong glass…Sir, it removed my veil from its gaunt head, rent it in two parts, and flinging both on the floor, trampled on them.”" This quote uses the mirror motif commonly featured in 19th century Gothic literature to enhance the doubling of Jane and Bertha's identities. Through staring at herself in the mirror while wearing Jane's wedding veil and ripping the veil in half, Bertha embodies Jane's repressed anger and her desire to escape the confines of marriage. Jane's longing for independence is finally enacted by Bertha at the end of the novel when she burns down Thornfield Hall, which symbolises a destruction of Mr Rochester's dominance over her identity.
Short stories.
"The Strange Case of Dr Jekyll and Mr Hyde" (1886).
Robert Louis Stevenson's novella "The Strange Case of Dr Jekyll and Mr Hyde" is a famous example of the Gothic double motif which explores the duality of man and the inner struggle between good and evil within the mind of an individual. In the novella, the physician Dr Henry Jekyll invents a medicine which allows one to separate their good and bad selves from each other, transforming into the evil and grotesque Mr Hyde when he takes the drug. Notably, Dr Jekyll's transformation into his evil double is not supernatural, but rather facilitated by a scientific experiment, reflecting the growing interest in science and psychology in the 19th century. However, much like the monstrous creation in Mary Shelley's "Frankenstein", this ambition of scientific discovery and advancement has disastrous consequences for Dr Jekyll as he is consumed by the evil within him. Stevenson's novella suggests that the desire to solve mysteries of the human condition through science are impossible, as Dr Jekyll is unable to control the evil aspect of his identity and his experiment ultimately fails.
The novella also comments on the awareness of drug addiction which emerged in the late 19th century, which was viewed as a mental and moral deficiency linked to the pursuit of vice. Mr Hyde is represented in the novella as the embodiment of addiction, a destructive and evil figure who unleashes chaos upon the life of Dr Jekyll, resulting in his suicide. Some interpretations argue that Mr Hyde is not a real figure but a hallucination of Dr Jekyll's, caused by his addiction to drugs and deviant behaviour which has resulted in psychological damage.
"The Yellow Wallpaper" (1892).
Charlotte Perkins Gilman's Gothic short story "The Yellow Wallpaper" utilises the double motif to explore the impact of patriarchal authority on the freedom of women. "The Yellow Wallpaper" is an example of the Female Gothic sub-genre through its use of the double motif to expose the fragmented and divided identities that women experience as a result of societal limitations in the 19th century. Written in an epistolary structure as a series of diary entries, the story is narrated by a woman who has been confined to an isolated manor in order to recover from postpartum depression, cared for by her physician husband who frequently dismisses her illness as trivial and made-up. Echoing Bertha Mason's imprisonment in the attic in "Jane Eyre", the narrator of "The Yellow Wallpaper" is similarly confined to an upper room of the manor which features a bright yellow Arabesque patterned wallpaper that she becomes increasingly obsessed with, spending hours trying to make sense of the confusing pattern. The narrator begins to experience hallucinations that the figure of a woman is creeping behind the wallpaper and shaking it as if she is trying to escape, as shown in the quotes below."This wallpaper has a kind of sub-pattern in a different shade, a particularly irritating one, for you can only see it in certain lights, and not clearly then. But in the places where it isn't faded and where the sun is just so – I can see a strange, provoking, formless sort of figure, that seems to skulk about behind that silly and conspicuous front design." 
"“The faint figure behind seemed to shake the pattern, just as if she wanted to get out.”" The narrator's schizophrenic hallucination is a metaphor for her divided identity controlled by the authority of her husband, in which the woman behind the wallpaper symbolises her repressed self, imprisoned within the patriarchal institution of marriage and motherhood. At the end of the story the narrator begins to identify herself with the figure behind the wallpaper so that their identities merge and become indistinguishable from one another, confirming that the figure represents her repressed double. This is shown when the narrator locks herself in the room and rips the wallpaper off the walls in an attempt to free the imprisoned woman, preparing a rope so that she can tie the woman up when she emerges from behind the wallpaper."I've got a rope up here that even Jennie did not find. If that woman does get out, and tries to get away, I can tie her!" This statement indicates that the narrator still views herself and the woman as separate people as she plans to tie the woman up, however, this distinction is soon blurred once she succeeds in ripping off the wallpaper. The quotes below demonstrate this final merging of identities between the narrator and the woman behind the wallpaper, in which her repressed self is liberated."I don't like to look out of the windows even – there are so many of those creeping women, and they creep so fast. I wonder if they all come out of that wall-paper as I did? But I am securely fastened now by my well-hidden rope...I suppose I shall have to get back behind the pattern when it comes night, and that is hard!" 
"'I've got out at last,' said I, 'in spite of you and Jane. And I've pulled off most of the paper, so you can't put me back!'" 
20th century.
Novels.
"Rebecca" (1938).
Daphne du Maurier's Gothic romance novel "Rebecca" uses the double motif to explore the inability of women to fulfil gender expectations in the 20th century, particularly the idea of a perfect wife. This is explored in the struggles of the unnamed narrator who, after impulsively marrying the aristocrat Maxim de Winter, experiences feelings of inadequacy when trying to measure up to the esteemed reputation of his deceased wife Rebecca. As the novel progresses, the narrator becomes increasingly obsessed with the ghostly memory