Background
"Love’s Philosophy" was written by Percy Bysshe Shelley and published in the year 1819. Shelley was a writer of lyrical romantic poetry. Some of his work was reprinted after his death in 1822.

Structure
This is a two-stanza poem, each consisting of eight lines. It adheres to an ABABCDCD rhyme scheme in each stanza, where the ABCD are unique to each of the two. The A rhymes in both stanzas are subtly imperfect. It is written in structure to establish the lyrical read of it. There is nothing abnormal to the structure. It follows common conventions with capitalization at the start of each line, comma placing, and use of semicolons. This is not atypical of romantic work from the period.

Analysis
The fountains mingle with the river
And the rivers with the ocean,
The winds of heaven mix forever
With a sweet emotion;

The poem begins with four lines describing how nature comes together. This implies that it is natural to be united, that nothing or nobody is or should be alone. It also shows a blanket connectedness, that all is connected to everything else through a chain. The chain shown here goes from a fountain to a river to the ocean. Wind is everywhere and, as being so, is connected to everything. The line that follows, "Nothing in the world is single;" directly states what the first four lines intended to show. It can be inferred that the speaker will testify love as another form of connection. This is also expressed as a "sweet emotion" in a fourth line. This exhibits some personification for the nature described at the start, as rivers and oceans do not feel emotion. However, this is used to make a point of union in nature and to set up the conveyance of the speaker’s emotion.

All things by a law divine
In one another’s being mingle; —
Why not I with thine?

The last three lines of the first stanza serve to further indicate the speaker believes love is an important relationship between people. He or she clearly believes everything in the world naturally share a relationship. The speaker is equating the connection between two people to that of different aspects of nature. In declaring these amorous feelings, the idea that intermingling with the object of affection should also be natural. The imagery of everything coming together was set up as an argument that the person the speaker loves should understand and, hopefully, reciprocate his or her feelings. It is especially compelling because it is through a law divine, or sacred law, that all bonds occur.

See the mountains kiss high heaven,
And the waves clasp one another;

Again, the speaker is making use of beautiful and vivid imagery to make a point. When looking at the peak of a mountain, it can indeed appear to be kissing the heavens. The speaker, however, is likely alluding to the idea of kissing the person to whom this poem is dedicated. In a similar fashion, the way the "waves clasp one another" is a way someone in love longs to hold a loved one. This goes hand-in-hand with the notion that the speaker is not only describing a beautiful scene in nature but also hinting at a desire. Just as different wonders in the world touch and bond this way, he or she longs to forge a similar relationship with the loved one.

No sister flower would be forgiven
If it disdained its brother;
And the sunlight clasps the earth,
And the moonbeams kiss the sea;

These lines further exhibit the attachment between everything. They serve to solidify the statement of the earlier line, "Nothing in the world is single." It is with that belief system that the lines, "No sister flower would be forgiven / If it disdained its brother;" are brought forth. Just as loyalty in the bond of family is so established, the speaker believes love should demonstrate the same loyalty. The speaker believes the two should intertwine and come together just as everything else and everyone else.

What are all these kissings worth,
If thou kiss not me?

The final lines insinuate this love is not reciprocated. This is in keeping with the rest of the poem, in which the speaker poses an argument using beautiful imagery and the nature of the world and its relationships. If the love were mutual, there would likely not be a need to make such a strong point in the declaration. This is accentuated in the final two lines, where the speaker finally admits it all pales in comparison to the kiss of the loved one. However, the poem ends with a question of significance. The speaker is pointing out that these other connections may be great and wonderful, but they crumble due to the fact he or she cannot receive true love’s kiss. Unfortunately, the speaker is single unlike the earlier line of the poem, "Nothing in the world is single." This poem establishes itself as an epitome of romance with such grand illustrations and emotions.

Summary
The poem details a feeling of longing through vivid description of the beauty in natural connections. Love, or simply a relationship, is represented through the depiction of nature. Many different elements and parts of the Earth come together in unexpected but great ways. It speaks of union, loyalty, and the importance of it. The poem also shows how the speaker is disheartened by seeing so much unity around but suffers and unrequited love.

Theme
The theme of this poem is the importance and the organic qualities of relationships. This is prominent through the imagery used throughout the poem as well as the declaration of love. The fact the love is likely unreciprocated also highlights the importance of relationships. The speaker feels dull and cannot appreciate the beauty of what is being described due to the feeling of rejection. It serves to push forth the idea that love and relationships are of the utmost importance in a person’s life.

References
– poets.org/poetsorg/poem/loves-philosophy