It is important to note how the Grecian urn that Keats contemplates acts symbolically in the poem. Throughout, it is regarded as a symbol of eternity or what is beyond time. Note how the speaker addresses the urn at the beginning of the poem:

Thou still unravished bride of quietness,

Thou foster child of silence and slow time,

Sylvan historian, who canst thus express

A flowery tale more sweetly than our rhyme...

It is worth analysing these images carefully to see how the urn operates in the poem. It is compared by a metaphor to an "unravished bride of quietness," indicating the way that, although it is so ancient, it is still pure and unsullied by the corrupting influence of time. It is described as a "foster child" of "slow time" and a "Sylvan historian." Clearly what the speaker admires and is seduced by is the way that it represents the eternal through the way that it has not been damaged by time and how it preserves history.

After the descriptions of the pictures of the urn, the final stanza cements the importance of it to the mind of the reaader:

Thou, silent form, dost tease us out of thought

As doth eternity: Cold Pastoral!

When old age shall this generation waste,

Thou shalt remain, in midst of other woe

Than ours, a friend to man...

I love the phrase "dost tease us out of thought / As doth eternity." It is as if viewing the urn is contemplating eternity, which in turn leads to peace or sadness as that causes us to think about the brevity of our lives. Thus ironically, the contemplation of the urn or of art can lead to an experience of the timeless or and at the same time the ephemeral nature of our own earthly existence. The poem can be thus said to have a bittersweet tone as these two contrary reactions are balanced together. Thus the longing for the permanent is expressed alongside the sombre recognition of our transient state.

In the poem Ode on a Grecian Urn John Keats remarks on the permanence of art against the mortal human life. Discuss with reference to the poem.

This poem celebrates the scenes and stories painted on the Grecian urn.  The speaker addresses the urn with several rhetorical questions and then proceeds to draw the conclusion that the subjects on the urn are sweeter and happier than the humans on earth.

The speaker first notes that

Heard melodies are sweet, but those unheard

Are sweeter; (11-12)

meaning that the mortal tunes on earth will fade, but the concept of musical beauty suggested by the urn will not.

He goes on the address the picture of the lover, just bending forward for a kiss from his lady.  The speaker acknowledges that he will never, ever get his kiss, but that this moment of expectancy and thrill is far more powerful than the kiss itself.  He tells the young man:

Bold Lover, never, never canst thou kiss,  

Though winning near the goal - yet do not grieve;       

She cannot fade, though thou has not thy bliss,     

For ever wilt thou love, and she be fair (17-20)

Even though they will never become full lovers, the will also never age, fight, argue, cheat etc.  In this way, love on the urn is much more permanent than love between mortal men.

The speaker goes on to assert that the people on the urn live in perpetual spring and are perpetually young; this does not happen in the "real world".  Finally, he notes in the final stanza that when we are all dead and gone, the urn will remain as truth:

Beauty is truth, truth beauty - That is all

Ye know on earth and all ye need to know (49-50)