This thesis is a study of James Hogg's use of structure and irony to achieve aesthetic and thematic unity in A Justified Sinner. Chapter one, for instance, explores the misleading and discrepant attitudes of the two narrators as they are apparent in their depiction of seventeenth- and early eighteenth-century Scotland. The second chapter involves a psychoanalytical study of the 'double' motif, and discovers a balanced source of double irony in considering the 'double' as indicative of the problem of narcissism and the problem of consciousness. The middle chapter elucidates two forms of irony in the theme of the relationship between knowledge and perception and in the thematic imagery with which the Faustian quest for special knowledge is parodied. Chapter four considers the relationship between allegorical and realistic modes of irony in the novel. The final chapter considers A Justified Sinner as a tragedy and as a comedy. In each case irony attends both sides of the apparent disunity, and helps significantly in achieving an underlying unity. The thesis concludes with a defense of Hogg's use of structure and irony in providing a satisfying resolution to the dilemmas raised in A Justified Sinner.