A reading of Shakespeare’s 31st sonnet
After the two preceding sonnets, Sonnet 31 seems like a bit of a comedown and, indeed, a let-down; yet it’s worthy of analysis because of its treatment of the idea of a love ‘dead’ and ‘buried’.
Thy bosom is endeared with all hearts,
Which I by lacking have supposed dead;
And there reigns Love, and all Love’s loving parts,
And all those friends which I thought buried.
How many a holy and obsequious tear
Hath dear religious love stol’n from mine eye,
As interest of the dead, which now appear
But things removed that hidden in thee lie!
Thou art the grave where buried love doth live,
Hung with the trophies of my lovers gone,
Who all their parts of me to thee did give,
That due of many now is thine alone:
Their images I loved, I view in thee,
And thou (all they) hast all the all of me.
In summary, Shakespeare tells the young man that he, the Fair Youth, now has the love and admiration of all the people who used to love him, Shakespeare; because these people have long since ceased to love Shakespeare, and Shakespeare’s love towards them has cooled, the poet had assumed those people were dead. All of love, in fact, now resides in the young man – including Love himself, in the form of Cupid, Roman god of love.
Shakespeare then tells us that when love has died in the past, he has shed many a tear at its passing, as though at a 
funeral. The Bard likens these tears to ‘interest’ paid to the dead – in another financial analogy left over from the previous sonnet – because it’s our duty to weep for those who have died. But these lost loves are not really dead – but they’re ‘out of sight, out of mind’, we might say, since the poet has ceased to have feelings for them. These loves have instead gone to lie in the charnel-house that is the Fair Youth: yes, he’s being likened to a sort of mass grave where all of Shakespeare’s past loves have been buried. This is because everyone who meets the Fair Youth ends up transferring all their love to him, because he is the most lovely and beloved of all men (and, presumably, all women too). And so, by association, the young man also has all the poet’s love too, since everyone he has loved now loves the Fair Youth.
A winding conceit, this, and perhaps not one to which every readerly bosom will return an echo. (Don Paterson, in Reading Shakespeare’s Sonnets: A New Commentary