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Wordsworth's poem The Solitary Reaper is illustrative of the Romantic poet's emphasis on the power of the imagination to transform simple objects/events of the everyday world into representations of an ideal reality.
The Highland girl in the poem is an example of the ordinary or humble pointing towards an ideal of unity or completeness of being. The reaper, working and singing is a flesh-and-blood human being who becomes "a spiritual gateway" for the speaker of the poem. Her simple song may be an expression of her own,but the speaker imagines it to be a melody of the eternal and the boundless, very much like "the still sad music of humanity" that the poet heard in his poem, Tintern Abbey. This intuitive and imaginative impression of the infinite leaves the speaker a different man than when he first saw the girl. Although the language of the girl's song is not known to the speaker, it lingers on as a lasting key to the universal everlastingness.
Wordsworth's poem thus explores the poet's conviction that the infinite can be perceived in the world of finite phenomena, and imagination alone can make that perception possible.