The speaker’s jealousy is one of the primary emotions driving “Catullus 51.” The presence and object of this jealousy are evident from the poem’s first lines, where the speaker considers Lesbia’s presumed lover to be “equal” (Line 1) or “better than gods” (Line 2). The speaker’s immediate acknowledgment that this comparison may be considered “blasphemy” (Line 2) demonstrates he is an otherwise pious man overtaken by emotion.

Part of the speaker’s jealousy is rooted in his emotional sensitivity. Rather than able to talk and listen to Lesbia as the man “who sits across from [her], and stares, and hears / continually” (Lines 3-4), the speaker finds himself struck “dumb” (Line 7) and unable to engage. The speaker, then, is not only jealous of the god-man’s implied romantic relationship with Lesbia, but of his ability to look at and listen to her. The speaker’s eyes, by contrast, “are veiled within / a two-fold night” (Lines 11-12) when he looks upon Lesbia, rendering him unable to see her. Likewise, his ears “ring with a bright / and tinny sound” (Lines 10-11), meaning he is likewise unable to hear her.

Catullus focuses on benign aspects of a romantic relationship—hearing and seeing one another—to demonstrate the depth of the speaker’s jealousy.