1) poetry is a waste of time;

4) poetry was banished from Plato's imaginary republic so it must be dangerous.
        
Four responses:

1) How can poetry be a waste of time if learning leads to virtue and poetry is the best way to learning?

Poetry serves a noble purpose--Poetry is better equipped to teach right behavior than either philosophy or history. Poetry shows history more brilliantly than history, and explains philosophy more cogently than philosophy.
Poetry has noble roots--much of the Bible is written in poetic form. Philosophy originally appeared in poetic form.
Comic poetry--holds vices up to such ridicule that no one would want to be like the ridiculous, vice-ridden characters portrayed therein.

        Sidney draws on various sources (most notably, Plato, Aristotle, Horace, and Scaliger) in defending poetry against the usual laundry list of charges.
        He begins by arguing that poetry may be found at all times in all cultures. The first artists and learned men were poets. Sidney gives as examples Musaeus, Homer, and Hesiod--three poets whose works are at the foundations of Western culture. Philosophy originally appeared in poetic form: Thales, Empedocles, and Parmenides wrote natural philosophy (the forerunner of our modern physical sciences) in verse, while Pythagoras and Phocylides wrote moral philosophy in verse. Plato--that famous banisher of poets and poetry--wrote using poetic devices such as metaphor, description, and dialogue. Even historians such as Herodotus relied on poetic techniques in writing their works.
        Sidney considers the prophetic (Latin vates) and creative (Greek poiein--to make) functions of the poet and of poetry. the poet (somewhat like the artist in Plotinus) improves upon nature: "Her world is brazen, the poets only deliver a golden."
        Sidney follows (with some embellishment) Aristotle in defining poetry as an "art of imitation," and he divides this imitation into three kinds:

3) "right poets" whose works "most properly do imitate to teach and delight, and to imitate borrow nothing of what is, hath been or shall be; but range only reined with learned discretion into the divine consideration of what may be, and should be."

        Sidney's primary assumption is that the end of learning (and by extension the end/goal of art) is virtuous action/behavior. Poetry is better equipped to teach right behavior than either philosophy or history. Philosophy deals in the abstract and the universal, but not in the particular. History deals only in the particular, not with general principles. Poetry deals with both, illustrating universal principles with particular examples or embodiments of those principles:
Now doth the peerless poet perform both: for whatsoever the philosopher saith should be done, he giveth a perfect picture of it in someone by whom he presupposeth it was done; so as he coupleth the general notion with the particular example.
Another advantage poetry has over philosophy is greater clarity:

the philosopher teacheth, but he teacheth obscurely, so as the learned only can understand him; that is to say, he teacheth them that are already taught. But the poet is the food for the tenderest stomachs, the poet is indeed the right popular philosopher.

Essentially, poetry shows history more brilliantly than history, and explains philosophy more cogently than philosophy.
        Sidney defends comic poetry by arguing that it holds vices up to such ridicule that no one would want to be like the ridiculous, vice-ridden characters portrayed therein.
        He goes on to defend poetry in general by pointing out that much of the Bible is written in poetic form. Nathan recalls David (and the reader) to virtue by telling a story; Christ teaches by means of parables which (when compared to unadorned didactic lectures) "more constantly . . . inhabit both the memory and judgment.
        Sidney then takes on four arguments against poetry:
1) poetry is a waste of time;
2) poetry is the "mother of lies";
3) poetry is the "nurse of abuse, infecting us with many pestilent desires"; and
4) poetry was banished from Plato's imaginary republic so it must be dangerous.
The first objection Sidney dismisses as begging the question. How can poetry be a waste of time if learning leads to virtue and poetry is the best way to learning? this counter-argument depends, of course, on the reader having accepted Sidney's earlier definitions of what constitutes poetry. The second objection (that poetry is the "mother of lies"--a phrase redolent with the Biblical associations to the Father of Lies, Satan himself) he answers by placing poetry outside of the realm of truth and falsehood: "for the poet, he nothing affirms, and therefore never lieth." Since the poet never claims that he is presenting absolute truth in the first place, the accusation of falsehood leveled at poetry is merely irrelevant. The third objection (that poetry abuses men's wits, leading them into temptation as it were--hearing an echo of Boethius here?) he answers by arguing that the abuse of any art (or thing) should not condemn that art: poetry is not to blame for the abuses committed against it by bad poets (if it were, college creative writing classes would have to be made illegal). the fourth objection (that Plato expelled poetry and poets from his republic) he responds to a bit slickly: he says that Plato banished "the abuse, not the thing," and that by being wary of poetry's power, Plato honored rather than condemned poetry.
        Sidney devotes some space to complaining about the laxness of English dramatists in conforming to the unities of space, time, and action, and then he goes on to a discussion of the merits of English as a poetic language.