To be a romantic, notes Fay's brother, "is to believe anything can happen to us." Despite sometimes remarkable odds, people find love and happiness in this world. The Republic of Love is a celebration of love as ordinary occurrence, and it is an ambitious task in this age of cynicism. The subject of love is treated neither with pure romanticism nor with out-and-out mistrust. Shields is very much aware of the fashionably dim view of love taken today. As Fay notes:

We turn our heads and pretend it's not there, the thunderous passions that enter a life and later its course. Love belongs in an amateur operetta, on the inside of a jokey greeting card, or in the annals of an old-fashioned poetry society . . . It's womanish, it's embarrassing, something to jeer at, something for jerks. Just a love story, people say about a book they happen to be reading, to be caught reading . . . They think of it as something childish and temporary, and its furniture—its language, its kisses, its fevers and transports— are evidence of a profound frivolity.

It has become foolish to believe in romance nowadays, yet Shields remains unfashionably optimistic about this universal quest. As the title indicates, Shields believes love to be "a republic, not a sovereignty" held in reserve for a chosen elite. Rather, nearly everyone loves and is loved at some point. Some of the critical reception for this novel pointed out that the characters are a little too happy to be fully believed, yet throughout their happiness is tempered by evidence of love's fragility. Although many of the couples are secondary characters, they are important for the many and various ways love can go awry: from illness, indifference, disillusionment, betrayal, and even death. It is hardly a Jane Austen novel in which everyone is paired off neatly in the end. This is an affirmation of modern love, with the emphasis on the modern.

Another important element in The Republic of Love is work. What we do for a living informs who we are, and Shields's characters like to work. They have vocations, projects, and creative undertakings, whether it is writing books about mermaids or menopause, cooking, making quilts, or growing garden mazes. They like to be busy, and Shields skillfully integrates this very important part of life into her fiction. Fay's book Mermaids of the Inner Mind, her project throughout the novel, is finally published in the last chapter. Their work is fulfilling but just like most of our jobs there are good days and bad. On bad ones, Tom finds his insomnious fans annoying, and Fay tires of mermaids after studying them for so long. "Their writhing bodies. Their empty unblinking faces shrieking for love . . . Not one of the mermaids she's seen has had a whit of intelligence about her." Now that Fay has escaped their solitary mer-fate and found love, they do not intrigue her like they used to, but she perseveres. In fact, she has this quote from Leonardo da Vinci, "Art lives from constraints and dies from freedom," taped over her desk at work, and she wonders if the same isn't true of love. While a case can be made that the mermaid's perpetual longing for love is symbolic of Fay's own state, Fay recognizes that her romance with Tom is the first time she has ever been "intelligent" about love.