Goldsmith offers very little information about the titular “mad dog.” The only description the speaker offers is that the dog is “found” (Line 13) in town, just like the “many” (Line 14) other stray dogs in Islington. The poem’s title characterizes the dog as “mad,” as do the neighbors who swear the dog “lost his wits” (Line 23) and went “mad” (Line 27) before biting the man. However, the final twist of the poem implies that the dog was actually innocent and was instead poisoned from biting the inwardly corrupt man.

With so little information provided, the dog serves more as a symbol than a clearly defined character. The dog represents and demonstrates how human beings interpret the world around them to fit their preconceived notions. The neighbors know that the dog and man “at first were friends” (Line 17) and that a “pique” (Line 18) or irritation between the two occurred before the bite. However, the neighbors conclude the dog must be “mad” because he bit “so good a man” (Line 24), without ever questioning whether the man caused the disagreement. The dog thus exposes how people are blind to their own biases and how they construe reality as they wish to see it.