This sonnet is one of the opening collection addressed to 'a young man.' It is a series of rhetorical questions that reflect on the theme of absence and the sadness at being apart. As the e.notes guide to the sonnets states it is a formal Elizabethan sonnet written within  the structure of fourteen lines and the iambic pentameter. It has three quatrians (four lines) and a concluding rhyming couplet that sums the poem up. The poem reflects on the paradox that he appears to be simultaneously two beings,, yet they lead separate lives and have separate identities. It uses alliteration in 'thou teachest' and 'time and thoughts' using the 't' sound and the oxymoron - the antithesis- of 'sweet' and 'sour.' I hopoe this helps!