Hogg’s depiction of Robert’s relationship with Gil-Martin now enters a new phase. Whereas he has previously hinted that Gil-Martin is the devil incarnate, he now opens up the possibility that he is a product of Robert’s increasingly deranged mental state. Many of the experiences he describes could be attributed to what would nowadays be diagnosed as paranoid schizophrenia. Though schizophrenia would not be described as a distinct syndrome until 1853, case studies reporting corresponding symptoms had begun to appear in Hogg’s time and Robert displays many of them. For example, delusions of grandeur (believing himself to be the scourge of God); delusions of persecution (believing that he is being pursued by a demonic agent); hallucinations (for example, Gil-Martin’s shape-shifting abilities); and paranoia. There are also correlations between Robert’s state of mind and dissociative identity disorder (see note for page 189).
Concepts of mental illness underwent a profound shift between Robert’s day and Hogg’s. From the Middle Ages into the 17th century, ‘madness’ was thought to be the work of supernatural forces; the result of demonic possession or witchcraft. By Hogg’s time, however, understanding had advanced. Whilst folk belief still retained some shreds of the old notions, physiological theories and the idea of insanity as a form of illness requiring treatment – the backbone of the modern approach – became established. Hogg achieves a masterful feat in combining both strands of thought in his portrayal of Robert's mental disintegration.