The initial premise for the series was to examine what superheroes would be like "in a credible, real world". As the story became more complex, Moore said Watchmen became about "power and about the idea of the superman manifest within society." The title of the series refers to the question "Who watches the watchmen?", famously posed by the Roman satirist Juvenal (as "Quis custodiet ipsos custodes?"), although Moore wasn't aware of the phrase's classical origins until Harlan Ellison informed him about them. Moore commented in 1987, "In the context of Watchmen, that fits. 'They're watching out for us, who's watching out for them?'" The writer stated in the introduction to the Graphitti hardcover of Watchmen that while writing the series he was able to purge himself of his nostalgia for superheroes, and instead he found an interest in real human beings.
Bradford Wright described Watchmen as "Moore's obituary for the concept of heroes in general and superheroes in particular." Putting the story in a contemporary sociological context, Wright wrote that the characters of Watchmen were Moore's "admonition to those who trusted in 'heroes' and leaders to guard the world's fate." He added that to place faith in such icons was to give up personal responsibility to "the Reagans, Thatchers, and other 'Watchmen' of the world who supposed to 'rescue' us and perhaps lay waste to the planet in the process". Moore specifically stated in 1986 that he was writing Watchmen to be "not anti-Americanism, [but] anti-Reaganism," specifically believing that "at the moment a certain part of Reagan's America isn't scared. They think they're invulnerable." Before the series premiered, Gibbons stated, "There's no overt political message at all. It's a fantasy extrapolation of what might happen and if people can see things in it that apply to the real America, then they're reading it into the comic...." While Moore wanted to write about "power politics" and the "worrying" times he lived in, he stated the reason that the story was set in an alternate reality was because he was worried that readers would "switch off" if he attacked a leader they admired. Moore stated in 1986 that he "was consciously trying to do something that would make people feel uneasy."
Citing Watchmen as the point where the comic book medium "came of age", Iain Thomson wrote in his essay "Deconstructing the Hero" that the story accomplished this by "developing its heroes precisely in order to deconstruct the very idea of the hero and so encouraging us to reflect upon its significance from the many different angles of the shards left lying on the ground". Thomson stated that the heroes in Watchmen almost all share a nihilistic outlook, and that Moore presents this outlook "as the simple, unvarnished truth" to "deconstruct the would-be hero's ultimate motivation, namely, to provide a secular salvation and so attain a mortal immortality". He wrote that the story "develops its heroes precisely in order to ask us if we would not in fact be better off without heroes". Thomson added that the story's deconstruction of the hero concept "suggests that perhaps the time for heroes has passed", which he feels distinguishes "this postmodern work" from the deconstructions of the hero in the existentialism movement. Richard Reynolds states that without any supervillains in the story, the superheroes of Watchmen are forced to confront "more intangible social and moral concerns", adding that this removes the superhero concept from the normal narrative expectations of the genre. Reynolds concludes that the series' ironic self awareness of the genre "all mark out Watchmen either as the last key superhero text, or the first in a new maturity of the genre".
Geoff Klock eschewed the term "deconstruction" in favor of describing Watchmen as a "revisionary superhero narrative." He considers Watchmen and Frank Miller's Batman: The Dark Knight Returns to be "the first instances ... of [a] new kind of comic book ... a first phase of development, the transition of the superhero from fantasy to literature." He elaborates by noting that "Alan Moore's realism ... performs a kenosis towards comic book history ... [which] does not ennoble and empower his characters ... Rather, it sends a wave of disruption back through superhero history ... devalue[ing] one of the basic superhero conventions by placing his masked crime fighters in a realistic world". First and foremost, "Moore's exploration of the [often sexual] motives for costumed crimefighting sheds a disturbing light on past superhero stories, and forces the reader to reevaluate—to revision—every superhero in terms of Moore's kenosis—his emptying out of the tradition." Klock relates the title to the quote by Juvenal to highlight the problem of controlling those who hold power and quoted repeatedly within the work itself. The deconstructive nature of Watchmen is, Klock notes, played out on the page also as, "[l]ike Alan Moore's kenosis, [Veidt] must destroy, then reconstruct, in order to build 'a unity which would survive him.'"
Moore has expressed dismay that "[t]he gritty, deconstructivist postmodern superhero comic, as exemplified by Watchmen ... became a genre". He said in 2003 that "to some degree there has been, in the 15 years since Watchmen, an awful lot of the comics field devoted to these grim, pessimistic, nasty, violent stories which kind of use Watchmen to validate what are, in effect, often just some very nasty stories that don't have a lot to recommend them." Gibbons said that while readers "were left with the idea that it was a grim and gritty kind of thing", he said in his view the series was "a wonderful celebration of superheroes as much as anything else."