Shelley argues that poetry produces good morals. He does not mean this in a didactic sense; rather, poetry generates good morality through imagination and delight. It is designed to take a reader outside of their own mind and put them in someone else’s shoes: “It awakens and enlarges the mind itself by rendering it the receptacle of a thousand unapprehended combinations of thought” (17). Poetry engages the mind by introducing new ways of thinking. Therefore, it does not narrow the mindset; it enlarges it by encompassing new ideas.

Although poetry does not moralize directly, Shelley says the idea of poetry is the idea of taking a person outside of themselves to see beauty, which produces goodness: “[t]he great instrument of moral good is the imagination” (17). When he writes about morality, he does not refer to a list of what the poet believes is right and wrong. To Shelley, morality is a universal truth. Ascribing only to the morals of one’s time is dangerous because society’s morals change, whereas the morality of poetry is constant. He calls out a few poets for attempting to overtly moralize, saying they failed in both their goals of creating good poetry and affecting moral good: “[T]he effect of their poetry is diminished in exact proportion to the degree in which they compel us to advert to this purpose” (18).