The fourth part of the essay, sometimes titled “Causes of Defect in English Poetry,” serves as the "examination" section of a classical argument. Sidney turns to the question of poetry in England. He notes that because it is disrespected, the only people who write poetry are “base men with servile wits...who think it enough if they can be rewarded of the printer.” Next, Sidney meditates on the best way to write poetry—real poetry, that is. He notes that imitation, exercise, and true inspiration are all necessary components for good verse. Sidney spends time praising poets of yore, including Chaucer and the Earl of Surrey, and then criticizes his contemporary playwrights.
In Section V, the "refutation" section of a classical argument, Sidney criticizes contemporary love poetry and its poor articulation of love. He stresses the importance of simplicity and naturalness in verse.
Continuing in Section VI, sometimes called “Capacities of the English Language,” Sidney argues that English is especially well-suited for natural, effective poetry. This serves as the "peroration" (conclusion) section of a classical argument.
In the final section, VII, “Capacities of the English Language,” Sidney uses a long, run-on sentence divided by semicolons to directly address to inspire his readers. He summarizes his previous argument, once again rebutting criticisms and affirming poetry's strengths. While Sidney begins the essay making modest claims for poetry and apologizing for it, by the end, he grants it the godly power to make humans immortal. This is the "digression" section of a classical seven-part argument.
Beginning in Section IV, Sidney turns away from the history of poetry towards its situation in 16th-century England. He states that he thinks the “very earth laments” the country’s lack of warmth for poetry, “and therefore decks our soil with fewer laurels than it was accustomed." In this hyperbolic statement, he equates a poet’s laurels with literal laurel trees, suggesting that a lack of poetry leads to blight. Alongside this hyperbole, however, is an understatement. As he elevates poetry's importance higher and higher, he diminishes his own accomplishments, noting that he did not strive for greatness, but “overmastered by some thoughts...yielded an inky tribute unto them." This deflects possible charges of self-importance, and suggests his humility.
Drawing on the established tone, Sidney meditates on the best way to write poetry—real poetry. In a famous line, he again compares poetry to horsemanship: “For poesy must not be drawn by the ears, it must be gently led, or rather it must lead." Although the metaphor is subtle, here, he suggests that the poet, like the horseman, must allow his mount to lead the process. He continues the metaphor: “the fertilest ground must be manured, so must the highest flying wit have a Daedalus to guide him." Poetry is both of the earth and the sky.
Further referencing Daedalus, the Greek craftsman and father of Icarus, he notes that the Daedalus “hath three wings to bear itself up into the air of due commendation; that is art, imitation, and exercise." He goes on to explain that these three arts must be synthesized to create original works: “For there being two principal parts, matter to be expressed by words, and words to express the matter, in neither we use art or imitation rightly."
Having elevated poetry once again, Sidney takes another opportunity to parlay a potential counterargument, analyzing further the defects of contemporary poetry and especially drama. Returning to a previous point, he writes that recent plays are quite poor, unfolding over days rather than a single day, and beginning at a strange point in the actions. Moreover, comedy and tragedy mingle, creating laughter without delight, and failing to teach through the comic aspects. However, he condemns the part rather than the whole, noting with a simile that these plays are “like an unmannerly daughter, showing a bad education, causeth her mother Poesy’s honesty to be called in question.” Again, poetry is personified as a mother.
Continuing this point in Section V, sometimes called “Defects in Lyric Poetry,” Sidney criticizes the “over-honeyed” diction of his peers. Using more similes, he describes poetry as an over-salted meal, and to non-Western people: “For now they cast sugar and spice upon every dish that is served at the table: like those Indians, not content to wear ear-rings at the fit and natural place of the ears, but they will thrust jewels through their nose and lips." He criticizes the emphasis on appearance rather than substance. The similes here are notable for their apparent racism, accusing Indians of poor aesthetic taste, as well as comparing bad poets to "primitive" peoples.
Conflating poetry and national identity, Sidney asks his fellow poets to focus more keenly on “matter and manner,” and to recognize the beauty of English grammar. Continuing Section VI with an essay previously titled “Capacities of the English Language,” Sidney notes that English allows for masculine and feminine rhyme, as well as caesuras in the midst of lines.
The final section of the poem builds on and summarizes these points, showing perhaps the most "poetry" of the essay as a whole. Sidney states that, in light of all the benefits of poetry, and the rejection of all its purported defects, it is time “no more to scorn the sacred mysteries of poesy; no more to laugh at the name of poets... no more to jest at the reverend title of 'a rhymer.’” Instead, he entreats readers to “believe” that “no philosopher’s precepts can sooner make you an honest man, than the reading of Virgil...to believe, with me, that there are many mysteries contained in poetry.. to believe [poets] themselves, when they tell you they will make you immortal by their verses." The long, run-on sentence, including many clauses, has a soaring effect, serving as the rhetorical crescendo of the essay as a whole.
Just like the style, the promises in the final section are hyperbolic, suggesting that those who believe in poetry will be placed alongside “Dante’s Beatrice, or Virgil’s Anchises." He follows this by cursing those who will still deface poetry: “thus much curse I must send you in the behalf of all poets; that while you live, you live in love, and never get favour, for lacking skill of a sonnet; and when you die, your memory die from the earth for want of an epitaph." Despite his claims of humility, Sidney here himself reveals his belief that his work, including this essay, will make him immortal.