What is the theme of "Ode on a Grecian Urn" by John Keats?

One major theme of "Ode on a Grecian Urn" is that a beautiful work of art brings comfort and joy to the viewer. In this poem, the narrator gazes at the picture on an ancient Greek urn. It shows a pagan springtime festival, with musicians and young lovers ready to kiss. As the narrator contemplates this scene, he becomes more and more ecstatic. How "happy" the scene is and always will be! It will always be springtime, the leaves will always be on the trees, the lovers will always be young and in love, the musicians will be always playing their tunes. The narrator, as his enthusiasm rises to a crescendo in the third stanza, repeats the word happy six times:

Ah, happy, happy boughs! that cannot shed

         Your leaves ...

And, happy melodist, unwearied,

         For ever piping songs for ever new;

More happy love! more happy, happy love!

         For ever warm and still to be enjoy'd,

                For ever panting, and for ever young ...

To the narrator, the scene of the vase captures immortality and eternal youth, two deep desires of the heart. Isn't this better to be a work of art, he thinks, than to face "breathing human passion" that can leave us sorrowful and unfulfilled?

Yet the narrator also wonders about the problems freezing time could bring: what about the town that has been emptied of its people for the festival? Won't it be forever "desolate?" Isn't the flip side of freezing the moment the danger of being caught in the wrong moment?

But the narrator quickly moves back to his ecstatic contemplation of the urn, praising it in the next stanza with exclamation points: "O Attic [Greek] shape! Fair attitude!" He ends by saying that when his own generation is old and gone, the urn will still remain and bring comfort and joy to future generations.