Percy Shelley uses traditionally Romantic natural imagery to conjure an impression of a world coupled up, blissful in its togetherness, with the final persuasive implication that, therefore, the listener should also want to be a part of this happy pairing. Barrett-Browning’s poem is less happy, more questioning of her lover and determined to convince them that she is always thinking of them, as though answering an unheard accusation of forgetfulness.
Shelley’s natural imagery creates a progressive sense of coming together. Verbs like “mingle”, “mix”, “kiss” and “clasp” are all sweet, gentle, even elegant, creating an impression of a caring and nurturing – and natural – relationship. He describes the inevitable increasing in size of the natural elements (“fountains”, “river”, “ocean”, all flowing together), echoing the longed-for relationship increasing in affection until it inevitable consumes the whole of their world. Barrett-Browning explores a similar togetherness through her natural imagery. Her opening line, “I think of thee!” is almost indignant, as though she has been accused of not doing so and is determined to prove herself. As this sonnet formed part of a series of private letters to Robert Browning during their courtship while she was an invalid and they were apart, it’s possible this is a response to a question from him about whether she thinks about him and misses him. Her description of the “wild vines about a tree” also reflects a partnership, but there are unsettling undertones. Although her “thoughts do twine and bud”, the description of entanglement is surprisingly physical. There are also connotations not of equality, but weakness. The “vine” needs the tree to climb, and potentially for survival, feeding from it. It also perhaps implies that there is a threat of suffocation as there is “nought to see/except the straggling green which hides the wood”, implying an underlying fear that the vines – her – will eventually overpower the tree – him – and destroy the relationship.
In both poems, the natural imagery progressively intensifies. Shelley’s elements grow in size, the mountains stretching up to heaven, the ocean being formed, heaven and earth finally joining together as the “moonbeams kiss the sea”. This anticipates the growth of affection and love between the couple, elevating it to a universal status. Barrett-Browning’s intensity, however, is almost painful at times, but also has sexual connotations. As she implores him to “renew thy presence”, the pace increases to a breathlessness which culminates in the climactic “burst, shattered, everywhere!” This triad, separated by caesura, echoes the intensity of sexual feeling she imagines, followed by the “deep joy” of peace. The final line echoes the first clause, a return to the impetus for the poem that creates a sense of closure, or fulfilment.
Shelley’s final line is likewise the culmination of his argument. His rhetorical question leads to a now all-but-inevitable answer. If the world is naturally paired together, for the listener to reject him would therefore be unnatural, even cruel. It’s telling that Shelley doesn’t use any aggressive or powerful living images in his poem – he doesn’t use animals or the fourth element of fire to convey his ideas, the closest he comes is the intensity of sunlight yet it simply “clasps” the earth. To be overly aggressive would weaken his syllogism. The elements themselves are paired into masculine and feminine, according to the classical categories. In the first stanza, air and water, the feminine, are explored. Then, in a perfect balancing act the second stanza uses earth and light, the masculine. Shelley’s rhyming, too, uses a combination of masculine and feminine rhymes. This, however, is not perfectly balanced, but becomes slightly more masculine towards the end (“earth”/”worth”, “sea”/”me”) as the final persuasion intensifies and his desire to control the outcome increases.
While Shelley becomes (slightly) more intense towards the end as he heightens his persuasion, Barrett-Browning’s final lines feel like a settling back, a release or relaxing after the intensity of the exclamation, or sexual expression. She writes using a Petrarchan sonnet form, positioning her poem as a traditional expression of love but also confining her love and passion in the regularity of its formal expectations. Conforming to external restraints, however, allows her vocabulary more freedom to express the bounds of her passion, almost as though she is within a safe space – the privacy of her letters to her lover – but still (just) within the bounds of propriety, as a Victorian woman must be. Barrett-Browning’s experience of love is also a deeply disruptive force, echoing the way many Victorian women must have felt. Having been told all their lives to err towards restraint, denying passion, to fall deeply and passionately in love is a dramatic and intense moment. Her natural imagery has echoes of the Bible’s ‘Song of Solomon’, using religious allusion to legitimise her feelings – the reference to the “palm-tree” and the use of the tree/vine feeding from one another. As Shelley uses his rhymes to become more persuasive, Barrett-Browning uses rhythm to become more forceful. In addition to the imperatives “renew”, “rustle”, “set thy trunk”, line 11 changes the rhythm, dropping momentarily out of the confines of the sonnet into a joyful passion with her lover.
Shelley’s pastoral poem with its persuasive tone makes love seem natural and inevitable, in a tradition of poems of this kind, contrary to contemporary social restraints which are unnaturally constructed. Given Shelley’s advocacy for free love and his scandalous sexual behaviour at the time, however, the natural freedom he is describing could be more self-serving, as the images point to the idea of union and the passion that Barrett-Browning describes, but not marriage. Both poets challenge contemporary expectations of romance governed by restraint yet, in part because of its directed nature and its passionate language, Barrett-Browning’s feels the more genuinely in love.
 “Syllogism” – a logical argument drawing a conclusion. In Shelley’s case, everything in nature is coupled together so it would be natural for us to do the same.