Futures in Lilacs - Robert Hass

I am reading the following poem today by Bob Hass.  I think he is talking about the timelessness of beauty/love/tenderness
-- that it passes from one generation to the other.

Futures in Lilacs

“Tender Little Buddha,” she said
Of my least Buddha-like member.
She was probably quoting Allen Ginsberg.
Who was probably paraphrasing Walt Whitman.
After the Civil War, after the death of Lincoln,
That was a good time to own railroad stocks.
But Whitman was in the Library of Congress,
Researching alternative Americas,
Reading up on the curiosities of Hindoo philosophy,
Studying the etchings of stone carvings
Of strange couplings in a book.

She was taking off a blouse,
Almost transparent, the color of a silky tangerine.
From Capitol Hill Walt Whitman must have been able to see
Willows gathering the river haze
In the cooling and still-humid twilight.
He was in love with a trolley conductor
In the summer of—what was it?—1867? 1868?

In his NY Times review of Bob Hass' book, Stephen Burt makes special mention of this poem in the following way:
Poets who write for a nation — whether appointed laureates or self-designated bards — must notice the literary history of their art, the social and political history of their country and their own personal histories, their private lives. They may even feel forced to choose among them. “Futures in Lilacs,” for example, portrays Walt Whitman first in literary history, as a posthumous inspiration to Allen Ginsberg; second, Whitman “After the Civil War ... in the Library of Congress, / Researching alternative Americas”; finally, Whitman pursuing an unrequited love for the “trolley conductor” Pete Doyle in “the summer of — what was it? — 1867? 1868?” Hass ends the poem there, with a sudden question, as if to ask when a poet’s hidden passion can matter more than the life of his times.
- The purpose of life is to sing