«The other two, slight air and purging fire,
Are both with thee, wherever I abide».
This sonnet continues and completes the idea of Sonnet 44, but here air and fire — symbolizing the poet’s thoughts and desires, respectively — are linked to the youth because the poet continuously thinks about and desires the young man.
The other two, slight air and purging fire,
Figuratively, the sonnet implies not so much direct communication as the telepathic exchange of emotions.
Alone, the poet “sinks down to death, oppressed with melancholy,” and does not recover until the youth sends his well-wishes and love back to him. However, the poet’s melancholic emotions are cyclical, for as soon as the young man sends back these greetings, the poet begins to think about and to desire the youth, and shortly he feels alone again.
English audio from YouTube Channel Socratica
Summary from Cliffsnotes.com