What makes the Odes of Keats unique is the way that they focus so much on the difference between the eternal quality of beauty and how it stands so utterly apart from the brief mortality of human lives. His Odes therefore act as powerful mediations about what it means to be human and how humans relate to beauty and react to it. In "Ode to a Nightingale," for example, it is clear that the song of the nightingale is an important symbol of the eternal beauty that only highlights the mortality and brief lives that men experience:
Thou wast not born for death, immortal Bird!
No hungry generations tread thee down;
The voice I hear this passing night was heard
In ancient days by emperor and clown...
The song therefore has rather a paradoxical impact on the listener, as it both elevates the speaker with its beauty but also depresses him with the reminder of his own mortality and how he is oppressed by "hungry generations." In "Ode to a Grecian Urn," the end of the poem points towards the relationship between truth and beauty:
"Beauty is truth, truth beauty,"--that is all
Ye know on earth, and all ye need to know.
The Odes of Keats are therfore unique in the way that they clearly create a relationship between comprehending beauty and key truths of what it means to be human. Keats suggests that part of being able to comprehend and enjoy true beauty is also to recognise that such beauty points towards the inescapable mortality of humans. His Odes therefore are at once a celebration of beauty and its impact on humans but also a reminder of the brief lives that humans have to experience and enjoy such beauty.