The adult poet stands on the hill at Windsor Castle and looks down on Eton College, where he had been a student. (Though it’s called a “College,” Eton students are between thirteen and eighteen years old.) As he watches the children playing on the banks of the River Thames he imagines the suffering and misery they’ll someday face, and he considers whether he should tell them what’s in store. In the end he decides they’ll all eventually face the miseries of adulthood, so it’s better now simply to leave them in their innocence — “Where ignorance is bliss, ’tis folly to be wise.”

Gray’s language is self-consciously poetic and his contorted syntax is demanding. When he asks “Father Thames,” a personification of the river,

Who foremost now delight to cleave
With pliant arm thy glassy wave?

it’s an exceedingly literary way to ask, “Who likes swimming the most?” Sentences often stretch over many lines, and Latinate inversions often put adjectives after nouns and subjects after verbs. This passage, for instance —

And ye, that from the stately brow
Of Windsor’s heights th’ expanse below
Of grove, of lawn, of mead survey,

— makes more sense in modern word order, “And you that survey [look over] the expanse of grove, lawn, and mead from the stately brow of Windsor’s heights.” It’s a short poem, so work through it patiently and make as much sense as you can.