For them no more the blazing hearth shall burn, Or busy housewife ply her evening care: No children run to lisp their sire's return, Or climb his knees the envied kiss to share. (21-24)
These are the lines where the speaker starts to imagine what the lives of the dead villagers were really like. They don't have fancy monuments over their graves, and no one wrote the story of their lives, so it's up to him to imagine what their past was really like. And it's a pretty cozy, homely image: nice fire in the fireplace, a wife there to fix supper, kids climbing into his lap when he gets home from work to get cuddled. But of course, this is all the speaker's imagination. Is this memory legit, do you think? Is it fair to project this kind of memory onto total strangers? Or is it a way of honoring them in spite of the fact that there is no record of their lives?
Nor you, ye proud, impute to these the fault, If Mem'ry o'er their tomb no trophies raise, (37-38)
The speaker wants to make sure that proud, snotty people don't turn up their noses at the poor folks from the village who couldn't afford to put up fancy monuments over their loved ones' graves. In fact, he personifies "Memory" here, saying that it was "Memory" that didn't put up the monuments, or "trophies." It's like he's trying to displace the blame.
Can Honour's voice provoke the silent dust, Or Flatt'ry soothe the dull cold ear of Death? (43-44)
The speaker reminds us that no amount of honor or monuments in tribute to the dead are going to bring people back from the grave. So what's the point of memorials, then, according to the speaker? Is there a point? What kind of memorial would work?
Perhaps in this neglected spot is laid Some heart once pregnant with celestial fire; (45-46)
The speaker imagines more about what the lives of the villagers were really like. Maybe—just maybe—there was a poet (someone whose heart was filled with "celestial fire") who lived here who just never had a chance to publish his or her work, and so we have no record of them. This kind of memory is purely hypothetical, of course—it's all a big "what if."
Some mute inglorious Milton here may rest, Some Cromwell guiltless of his country's blood. (59-60)
Another hypothetical: what if a poet as awesome as John Milton (who wrote Paradise Lost) had lived and died here, totally unknown and undiscovered? What if someone with the passion and ambition of Oliver Cromwell (the guy who ran the English Commonwealth after the assassination of King Charles I) lived and died here, but never had a chance to fulfill his ambitions?
Their name, their years, spelt by th' unletter'd muse, The place of fame and elegy supply: (81-82)
Instead of a fancy monument or a literary biography, all these dead villagers get is a simple tombstone—badly spelt—with their names and the years that they lived and died. According to the speaker, does this mean that we should forget about them?