1. I want to know more about the doppelganger in The Unicorn, especially whether or not it is a major theme in Murdoch's modernist novel. 2. Is...

Doppelganger in The Unicorn
Marian thinks of "a ghost or a doppelganger" in Chapter 19 as she realizes "something or someone" was missing from the gold-winged scene around the mantel in Hannah's room where Gerald beneficently spreads welcome throughout what they accept as his "family." Marian, drinking whiskey neat, as they all are thanks to the attentions of Jamesie, contemplates the golden-glowing collection of people and realizes that there is an absence, then recognizes that it is Denis's face she doesn't see. Immediately after, Denis comes into focus. He is standing outside the circle of "winged" light in a black shadow that matches his black aspect, darkening eyes, disheveled shirt and shadow-darkened form. In this condition, Denis is another version of himself, a distorted version that is unrecognizable and incomprehensible to Marian. Metaphorically, Denis is his own doppelganger, a ghostly double of his still living self: smoldering darkly in a shadow, he is himself a dark shadow, a dark apparition.

Effingham's accusing, remorseful thoughts in Chapter 20 as he broils over what he could have, should have, might and would be allowed to do portray him as a doppelganger of himself: two selves tearing at each other in his suffering mental tirades. Effingham psychologically tears himself in two as he relives how he came to embrace such a foolhardy plan as helping Marian to affect Hannah's escape by fleeing with her on a plane; as he criticizes himself for a fantastical idea of how Hannah would react; as he ridicules his cowardly mode of escape after the Humber had been stopped by Alice at the gate; as he contemplates the sickening idea of how much harm had been done. He was torn in two: a self and an accusatory self, endlessly reprimanding the "horrible loutish idiocy" of that escape fantasy.

The whole plan ... was hopelessly ill-conceived. Hannah would never have consented to be taken away in a hurly-burly .... He had put Hannah in peril, laying her open to retribution from people who had power over her, he had almost certainly helped Marian to get herself the sack ... and worst of all he would himself be under sentence. (Chapter 20)

Doppelganger Theme
The incidents in chapters 19 and 20 do establish the doppelganger symbol as a theme in The Unicorn: Marian perceives the presence of "a ghost or a doppelganger" in Chapter 19. There are at least three characters who are manifested as doppelgangers by events following the attempted kidnapping of Hannah: Denis, Hannah and Marian.

Marian becomes a doppelganger, a ghostly apparition, of herself when, after the failed escape plan, she offers no resistance to Gerald in the "dark room": "She had been taken to some place of ultimate surrender ... in that dark room ... [and led] back chastened into the bright approval ...."

Hannah, now "wearing a peaceful ecstatic look" after the "ill-conceived" escape in the Humber, seems to have reclaimed her purity because she is returned to the safety of her surrounding walls. Yet her purity is as non-substantial as the golden-light around the group gathered at the fireplace. This ghost of purity exists because she depends upon her imprisonment, the suffering of others and the domination of Gerald to seem pure: her purity is an apparition, a doppelganger, of her true self.

Denis ought to be seen by Marian as part of the golden group "sheathed" in light, but he is not. He is isolated, darkened, hidden in a dark corner: "Denis's [face] was black ... like blackened iron. ... His eyes were black and his mouth a black line." Denis is a dark apparition of his true self because of the affects upon him of the realities behind Hannah's condition of imprisonment (Gerald and others' suffering), which is symbolized by his appearance: "His shirt was hanging open, his hair tousled."

Since the doppelganger theme is expressed in these three characters, you might also explore whether Jamesie or others further represent the doppelganger theme of divided authentic and inauthentic selves.

Psychological Distortion
Murdoch is considered a postmodernist writer, with The Unicorn published in 1963. The psychological distortion of the characters in The Unicorn has two explanations. The first is that the psychological distortion is key to the doppelganger theme since it shows the interior divide between psychological authenticity and inauthenticity; between purity and false purity; between the unicorn and the false unicorn. The second reason is that postmodernists perceive all of humankind as having fragmented consciousness, as having a distortion of and fragmentation between perception of self and representation of self. This fragmentation between perception and representation is illustrated by Effingham's inner monologue (Chapter 20) as he chides and berates himself and nearly doubles over, sickened, at the thought of the consequences he has brought down upon himself and others.

Ana Antunes Simão, "Gothicizing Morality"

Florence Howe, 1963 Iris Murdoch essay on The Unicorn