Dylan Thomas, partly because of his legendary status as a hard-drinking, wild-living Welshman, is often considered to be a primitive poet, one for whom poems somehow appeared on the page, almost miraculously springing up fully developed out of his passionate nature. In actuality, the contrary is true. Thomas's poetry is very carefully crafted, and he often uses complicated structures.

"Do Not Go Gentle into That Good Night" is an intricately structured villanelle, made up of five tercets, a unit of three lines of verse, followed by a quatrain, a unit of four lines of verse. The opening line of the poem, the first line in the first stanza, also ends the second and fourth tercets. The third and final line of the first tercet serves as the last line in the third and fifth stanzas. They will also become the last two lines of the quatrain.

The entire...