Replying to a ‘Lady’, Shelley's letter, written in 1821, makes an attempt to delineate the precise nature of the challenge of writing poetry. Opening with an insistence on the seriousness of being a poet, Shelley emphasises the amount that his addressee will need to learn in order to become an artist. Language, for Shelley, is a ‘sacred talisman’ (Letters: PBS II . p. 277) that requires an ascetic level of effort from the apprentice, who must ‘sacrifice many hours’ in order to understand and employ words. Yet the letter's brevity and its focus on language render it subordinate, in terms of both its content and style, to the more intense exploration of poetry and imagination housed in The Witch of Atlas and A Defence of Poetry. Such seriousness, at first glance, might seem antithetical to The Witch of Atlas. It may seem a frolic of a poem, the poet on holiday, as it fizzes with an infectious comic energy. But there is also a serious preoccupation with the difficulty of writing poetry that will last. If the poem plays a game, the game is one in which the stakes are high, as Shelley engages with the role, scope, and uses of poetry within the poem itself.

Similarly, A Defence of Poetry does not behave as a description of the art of poetry. Rather, Shelley challenges himself to embody the spirit of poetry in his prose. A Defence offers a theory of poetry that resists the creation of hard and fast definitions in favour of an exploration of the subtle interplays between the mortal and the immortal, poet and reader, poet and language. Shelley's Witch of Atlas offers a parallel exploration of these prose ideals, foreshadowing, considering, and representing A Defence's subtleties and flux. Moving far beyond the letter's preoccupation with language, the poem and prose essay meditate on poetry, imagination, morality, belief, poetic peers, and beyond in ways that reveal Shelley's subtlety and mobility.

The letter to a Lady assumes the tone of instruction without condescension. Carefully tracing the level of commitment required by poetry, Shelley constructs a short letter that succinctly offers guidance calibrated to encourage while preparing his reader for the challenge of art.