An allusion is a figure of speech that refers indirectly to a text, object, or event. Allusion differs from a reference in that the latter refers in explicit terms, whereas the former refers indirectly. The constant use of allusions in Ars Poetica reflects Horace’s insistence on a comprehensive knowledge of the traditional literary canon. He writes, “The poet, who first tried his skill in tragic verse for the paltry [prize of a] goat, soon after exposed to view wild satyrs naked, and attempted raillery with severity, still preserving the gravity [of tragedy]” (Lines 220-74, Paragraph 1). Horace uses both references and allusions, as in the quotation above where he does not explicitly name which poet to which he refers. An example of Horace using reference is in his passage on “madness,” wherein he says, “Empedocles, while he was ambitious of being esteemed an immortal god, in cold blood leaped into burning Aetna” (Lines 453ff, Paragraph 1).

Ekphrasis is the literary device of vividly describes a visual object or work of art. An author who uses ekphrasis implies a connection between the textual and visual arts. In the first lines, Horace’s description of a painting functions as an introduction to the theme of unity that pervades the poem.