To compare great things with small.

The phrase is commonly used as a concise rebuke to disproportionate analogy: it flags the error (or rhetorical impropriety) of measuring something grand, serious, or consequential by the yardstick of something trivial. In literary-critical terms, it points to a mismatch of scale—an inapt simile or comparison that diminishes the “great” subject or inflates the “small” one. As a standalone maxim it can also be read more neutrally, as a reminder that comparisons require commensurate terms; otherwise the comparison misleads rather than clarifies. However, without a verified Virgilian locus, its precise nuance in Virgil’s own usage cannot be responsibly specified.