This thesis reconsiders the perception and status of pets in eighteenth-century Britain through an analysis of the unconventional modes of representation in Thomas Gainsborough’s portrait of Henry Scott, Third Duke of Buccleuch. By examining the social attitudes towards pets in eighteenth-century Britain, this thesis discusses the elevated status of dogs in Britain’s early modern visual culture, which offers new possibilities for understanding the complex and sympathetic relationship between owners and their pets. By reconstructing the identity of the Dandie Dinmont dog in Gainsborough’s portrait of Henry Scott, this thesis provides an alternative narrative for the painting in which the dog is acknowledged for its near-equal role of importance in relation to the human subject. Contemporary discourses on animal ethics and posthumanist theory, as well as early modern philosophies, will be applied to the analysis of the portrait, with a primary focus on the influential writings of the eighteenth-century philosopher, David Hume. Gainsborough’s rejection of iconographic convention, which complicates the categorization of the portrait within a specific subgenre of portraiture, will also be discussed.