How then can a "Cold Pastoral" be called a "friend to man" in the poem Ode on a Grecian Urn?

The image that absorbs Keats (or, more precisely, the poem's narrator) on the Grecian urn is a "Cold Pastoral" because it is a picture frozen in time of a pastoral or outdoors scene. It is not something alive. It is cold, a piece of pottery, not warm like human flesh. Unlike human life, it will never change. Yet, paradoxically, it is a "friend to man" precisely becauseit will not change. Keats becomes ecstatic about...

The image that absorbs Keats (or, more precisely, the poem's narrator) on the Grecian urn is a "Cold Pastoral" because it is a picture frozen in time of a pastoral or outdoors scene. It is not something alive. It is cold, a piece of pottery, not warm like human flesh. Unlike human life, it will never change. Yet, paradoxically, it is a "friend to man" precisely because it will not change. Keats becomes ecstatic about the image on the urn being "happy" because the lovers depicted are forever destined to be young and in the full bloom of love, because it will always be spring there, and because it will always be a festival day on the urn. He contrasts this to human life, in which people fall out of the first raptures of love, then age, have problems, and die. Therefore, as Keats says, "When old age shall this generation waste" (in other words when he and his friends get old), the urn "shalt remain, in midst of other woe/Than ours." It will, he means, outlive the narrator's generation and be there for other people, yet unborn, who have their own problems, and who will need to escape from them as he has into the timeless beauty of the urn. Thus, Keats writes, the urn will remain:

a friend to man, to whom thou say'st,

         "Beauty is truth, truth beauty ..."

In other words, it will be a friend because, no matter how unhappy we are, it will continue across the generations to remind us of beauty and the truth in beauty.