A second part of the essay that serves as "proposition" section of a classical argument begins as Sidney writes, “Now let us go to a more ordinary opening of him, that the truth may be more palpable.” He turns away from the ancient names of poets and begins to describe poetry’s function—its "works" rather than its "parts." He asserts that its central function is to teach and inspire. Then, Sidney imagines two potential challengers to this elevating of poetry above all other forms of learning: the philosopher and the historian. He seeks to discount their two respective opinions.
Sidney notes that philosophers teach, but their teaching is too abstract. As for historians, whereas history also has particular examples, the poet is free to write about events as they should be, whereas historians can only talk about what was, and are thus “captive to the truth of a foolish world.” Poetry can draw on history, but poetry make history's lessons even clearer and more delightful.
To prove his point further, Sidney states that even Christ used poetry to convey his teachings: his parables provide specific illustrations of moral lessons. The poet is the “popular philosopher,” teaching in ways that are easily digestible. Finally, Sidney concludes the section by noting that poets not only teach readers, but also move them, a harder task than merely teaching.
Section III, sometimes called “The Poet Monarch of all Human Sciences,” serves as the "division" section of a classical, seven-part argument. Sidney extols the beauty of poetry, and its aptitude for teaching. Then, Sidney returns to a different idea: the distinction between poetry’s works or deeds on the one hand, and its “parts” on the other. As his argument progresses, we see that by “parts” he means genres of poetry. Sidney proceeds to praise the pastoral, the lamenting elegy, the iamb, the satire, the comic, the tragedy, the lyric poem, and the heroic poem.
This leads Sidney to consider possible counterarguments. First, he takes on the perspective of “poet-haters” who scoff without reason or understanding. After quickly dispensing with this counterargument, Sidney provides three more possible objections: “First, that..a man might better spend his time in them than in this. Secondly, that it is the mother of lies. Thirdly, that it is the nurse of abuse, infecting us with many pestilent desires.”
After addressing these three arguments, Sidney turns to a more serious adversary than “poet-haters”: Plato. Returning to a familiar argument, Sidney ultimately states that Plato took exception not to poetry, but to poets. After listing a number of admired ancient poets, including Socrates, Aristotle, and Plutarch, Sidney writes that he needs “not to defend poesy with the help of his underling historiographer.” He summarizes his argument once again.
Before Sidney seeks to defend poetry's "works," he elaborates on which kind of poetry he is talking about. The different forms of poetry are divided into three categories. The first category includes the religious poems and psalms mentioned in the Bible. The second category is represented by philosophical poems, and the third are poets who are a bit different than the philosophers. While philosophers paint nature accurately, the third class of poets “borrow nothing of what is, hath been, or shall be; but range only...into the divine consideration of what may be, and should be." Through this work, they teach their readers to be good. Sidney notes that poets of this third type of poetry may or may not be in verse, and that not everything in verse is poetry. However, true poets choose “verse as their fittest raiment."
He next seeks to judge poetry according to its “works” rather than its “parts.” He counts amongst poetry’s works or effects as “purifying of wit, enriching of memory, enabling of judgment, and enlarging of conceit”—in a word, enabling learning. While poetry has a different focus than astronomy, philosophy, etc., it devotes itself to the highest kind of knowledge: giving man knowledge of himself. He continues with the metaphor of horsemanship, noting that the horseman’s purpose is soldiery, and the soldier's purpose is to “perform the practice of the soldier.” This anecdote is meant to demonstrate that “the ending of all earthly learning [is] virtuous action."
Then, Sidney presents counterarguments through the eyes of historians and philosophers. First, he imagines philosophers approaching him with their “sullen gravity” and asking how poetry can teach morality better than philosophy when philosophy’s goal is to define virtue and design the best-ordered society. Next, he imagines historians, “laden with mouse-eaten records,” countering that philosophy is abstract, failing to account for real-world conditions, whereas history truly shows how one can learn from the past to take correct action.
Sidney says that there are four people concerned with man’s goodness: the historian, the philosopher, the lawyer, and the poet. The lawyer, however, focuses on preventing ill rather than cultivating good. Therefore, only the poet can serve as a moderator between the historian and the philosopher. The philosopher tries to encourage good with “precept,” the historian with “example,” but neither are able to implement both. The poet links and transcends the other two by giving a “perfect picture of...whatsoever the philosopher sayeth should be done."
Sidney brings up a number of examples to support his point, again using logos: “wisdom in temperance in Ulysses and Diomedes, valour in Achilles, friendship in Nisus and Euryalus” all provide specific examples of ideal virtuous actions, instructing man on how to act more effectively than can the philosopher. He quotes Horace: “Mediocribus esse poetis Non Di, non homines, non concessere columnae (Neither men, gods, nor lettered columns have admitted mediocrity in poets).”
In the next section, Sidney continues to defend this point. He notes that verse can make ugly things beautiful, and inspire men to feats: even average men “have found their hearts moved to the exercise of courtesy, liberality, and especially courage.” To prove his point, he mentions two historical uses of allegory that have had a significant effect. First, he points to Menenius Agrippa’s parable of a body that starved its belly because it believed it took too much, a parable that healed a divided Rome. Second, he states that Nathan the Prophet used the story of a lamb taken from its shepherd to show David the sin in his adultery. This thus constitutes a kind of meta-allegory, where the very success of these allegories is—in and of itself—an allegory for the effectiveness of poetry.
As Sidney turns to evaluating poetry's parts, he praises many genres as unimpeachable. However, his discussion of the comic raises several potential objections. Using a simile, he notes that comedy is like geometry: “the oblique must be known as well as the right.” That is to say, we must witness the evil as well as the good, and comedy helps us to see our own negative nature. Sidney reserves particular praise for the heroic, noting that its images “inflameth the mind with desire to be worthy.” He concludes that poetry is an ancient, venerable art that does no evil and has no bad parts.
Turning to poet-haters, he speculates that the main source of their humor is “rhyming and versing” (rhyme and meter). Sidney defends versification as a kind of music, as well as an aid to memory. He notes that most men memorize some couplets, providing as an example “Percontatorem fugito: nam garrulus idem est” (Fly from the inquisitive man, for he is a babbler).
Sidney lists three common objections to poetry: that it is useless, that it is "the mother of lies," and that it is corrupting. Sidney spends the most time considering the second objection, which could be argued to underly the others. Ultimately, he argues that poets are the ones who lie the least, because their aim is not to transmit truths but rather to convey feelings: “the poet, he nothing affirmeth, and therefore never lieth." Against the third objection, the claim that poetry infects us with lust, Sidney argues that if this happens it is the fault of the poet, not his medium. Using the rhetorical device of chiasmus (reversing the terms in a phrase), Sidney argues that we should “not say that poetry abuseth man’s wit, but that man’s wit abuseth poetry."
This section ends with Sidney expressing his belief that poetry will continue to exist even if there are people who fight against it. He begins by reminding the reader of Plato’s own poetry: “if he will defile the fountain out of which his flowing streams have proceeded, let us boldly examine with what reason he did it.” The first idea Plato raises is that philosophers are jealous of poets, who are in a sense their “ungrateful apprentices,” getting praise for forwarding ideas that stem from philosophy and moreover holding exalted social positions while philosophers were banished from their kingdoms. He briefly suggests Plato might have banished poetry for its femininity, but quickly acknowledges that poets were, in fact, allowed in the republic. "Plato found fault that the poets of his time filled the world with wrong opinions of the gods." Sidney is thus able to argue that, according to Plato, poetry could affect how people felt about the gods—a skill which could also be used for good. Using a metaphor, Sidney argues that those who object to poetry under Plato’s banner misrepresent him and abuse his authority, as if “under [Plato’s] lion’s skin they would make an ass-like braying against poesy.”