The central theme of Closer revolves around truth. All the characters have a tense relationship with truth—only Alice is "not passionate about veracity". Truth, for Dan, is what distinguishes humans from animals—and yet Alice accepts her identity as not quite human for any of the other characters, and loves her primitivism. Arguably, her inability to deal with the truth causes her to leave Dan at the end. Those who are passionate about veracity press each other to tell the complete truth, no matter the emotional pain caused by it—and the controlling irony of the situation is that though the truth clarifies, it does not bring together. No one is made "closer" by the truth.
Also being challenged and taken apart is the illusion of love and romance. Dan, the failed writer, speaks in romantic language but feels the least qualms about his infidelities. The characters are driven both by a need for love and a need for sex—these needs clash at times, as when Larry tells Dan that Alice needed love, and Dan had left her for a relationship with Anna. The mythic constructions surrounding personal relationships—the myth of love and truth bringing us together, is deliberately and wilfully turned on its head by Marber.
Closer has been described as a work that "gets under its audience's skin, and ... not for the emotionally squeamish", a work in which "Marber is alert to the cruel inequalities of love, as the characters change partners in what sometimes comes over like a modern reworking of Coward's Private Lives."