Shelley's "Defence of Poetry" makes me proud to be a person who tries to write poems.

Language, colour, and religious and civil habits of action, are all the instruments and materials of poetry; they may be called poetry by that figure of speech which considers the effect as a synonyme of the cause. But poetry in a more restricted sense expresses those arrangements of language, and especially metrical language, which are created by the imperial faculty, whose throne is curtained within the invisible nature of man. And this springs from the nature itself of language, which is a more direct representation of the actions and passions of our internal being, and is susceptible of more various and delicate combinations, than colour, form, or motion, and is more plastic and obedient to the control of that faculty of which it is the creation. For language is arbitrarily produced by the imagination, and has relation to thoughts alone.

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Poetry is a mirror which makes beautiful that which is distorted.

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A single word may be the spark of inextinguishable thought.

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Poetry strengthens the faculty which is the organ of the moral nature of man, in the same manner as exercise strengthens a limb.

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Poetry is not like reasoning, a power to be exerted according to the determination of the will. A man cannot say, "I will compose poetry." The greatest poet even cannot say it; for the mind in creation is as a fading coal, which some invisible influence, like an inconstant wind, awakens to transitory brightness; this power arises from within, like the colour of a flower which fades and changes as it is developed, and the conscious portions of our nature are unprophetic either of its approach or its departure.

All of this feels true to me. No doubt someone with excellent arguing powers could prove otherwise, but the creation of poetry has nothing to do with argument. I especially love the final line I've quoted: "the conscious portions of our nature are unprophetic either of [creation's] approach or its departure." I agree: any real poem I've written has crept in through an unlocked, unwatched door.