In fact, in lyric poetry, truthfulness becomes recognizable as a ring of truth within the medium itself.

Heaney is distinguishing poetic “truth” from factual accuracy. In lyric poetry, he suggests, truthfulness is something the reader can hear and feel as an internal rightness—an earned authenticity produced by the poem’s language, rhythm, and tonal integrity. The “ring of truth” implies a test like striking metal: the medium itself resonates when the poem’s utterance is honest, even if it is imaginative, compressed, or metaphorical. The remark also points to Heaney’s broader concern with ethical speech in art: lyric may not report events, but it can still be answerable to reality through precision, emotional candor, and a voice that convinces by its own coherence.