In its form, "On His Having Arrived at the Age of Twenty-Three" is an Italian sonnet (also known as a Petrarchan sonnet), written, like most sonnets, in iambic pentameter. Its thematic organization closely follows the structure of the form, with two well-developed movements corresponding to the eight-line octave and the six-line sestet. The octave follows the conventional Petrarchan rhyme scheme of abbaabba, while the sestet rhymes cdcdee, one of several conventional patterns. The octave breaks conventionally into two shorter movements, each consisting of a quatrain rhyming abba. The beginning of the sestet, where the rhyme scheme changes, is known as the turn of the sonnet because at this point an Italian sonnet's theme or tone usually shifts. In the case of "On His Having Arrived at the Age of Twenty-Three" the transitional "But" signals a change from the impatient arrogance of the octave into the humbler prayer of...