Question

identifying the central idea
so long as men can breathe or eyes can see,
so long lives this, and this gives life to thee.
— \sonnet 18,\
william shakespeare
in one to two sentences, explain the central idea of the final couplet of the poem.

Explanation:

The final couplet of Shakespeare's Sonnet 18 centers on the enduring power of poetry: it asserts that the poem itself will keep the subject alive and remembered for as long as humanity exists to read and perceive it.

Answer:

The central idea of the final couplet is that the poem (the "this" referenced) will grant eternal life and remembrance to the poem's subject, as it will endure as long as there are people who can read and experience it.