William Shakespeare’s Sonnet 116 is one of his best known sonnets, tackling the elusive and timeless question of the nature of true love. The sonnet is a part of the "Fair Youth" grouping, and employs the English form, with an abab cdcd efef gg rhyme structure, as well as trademark iambic pentameter. The argument of the poem is that true love, a “marriage of the minds” is “an ever-fixed mark.” That is to say, true love will not alter, wither, or fade, despite impediment, calamity, or the ravages of time upon beauty.
While modern readers often associate the Fair Youth poems with a notion of physical or passionate love, Sonnet 116 actually deals with what is considered lofty love, love that does not necessary involve physical expression. The fact that the love spoken of is introduced as the “marriage of true minds,” establishes that the form of love that is being spoken about is a mental construct, rather than physical or sensual.
Shakespeare goes on to claim that there is no real impediment to true love, it is timeless, impenetrable, beyond fixed value, and thus not constrained to the realm of the body.
The first quatrain establishes what love is not. It is not susceptible to impediment, alteration, removal. The second relays what love is: fixed, unshakeable, a guiding light, immeasurable in worth. The third relates love to time, or rather proves it impervious to it. Time may fade beauty, but a love that “is a marriage of the minds” will not be changed. It will continue until death, says the final line “But bears out even to the edge of doom.”
Sonnet 116 employs a "turn" at the end of the sonnet, a device which structures the poetic intent and gives clues into the way it should be interpreted. The turn is the point where the focus changes. This can be in the sense that the sonnet moves from question to resolution, provides a purpose for the poem, or can be an unexpected element that changes or upends the meaning of the portion that came before the turn.
Here, the turn creates a paradox, stating that if the poet is wrong on his interpretation of love, then neither his love nor his poetry of love has any place within the world. Throughout the poem, Shakespeare has laid out his assertions regarding what true love is and is not.
This sonnet is a quintessential example of the "Fair Youth" sequence, a grouping of Shakespeare's sonnets that celebrate a young man. In this sense, the marriage of the minds could also be speaking of a non-sexual form of devotional love. Thus the end lines speak to a singular love on the part of the narrator for the young man, rather than a generalized mankind, in “no man ever loved.”
What Shakespeare is doing is presenting a personalized argument that both love and poetry are able to withstand the ravages of time. If he can be proved wrong, then he has obviously misunderstood the concept, and thus cannot be considered to have either really loved or have written true poetry.