The struldbrugs are totally unique to Luggnagg. Gulliver is introduced to this term by "a person of quality" (3.10.2). (Gulliver loves speaking to people of quality, i.e., people of the upper class. Snob!) This unnamed person of quality asks Gulliver what he would do if he could live forever? Gulliver really likes this idea. He says he would make tons of money, learn everything there is to know in the world, and then spend all of his time talking to other immortals, who must be equally as brilliant as he would be.
The person of quality laughs at Gulliver's stupidity. The thing is, Luggnagg has immortals, the struldbrugs. Perfectly ordinary parents can have them, and they are marked by a dot above the left eyebrow that changes color as they grow older until it hits black at age forty. Oddly, the struldbrugs tend to have normal, mortal children.
These immortals, unlike our fantasies of, say, Edward Cullen in Twilight or Vampires Bill and Eric in True Blood, are not eternally young. They age normally up until age eighty, when, the Luggnaggians imply, most decent people have the sense to die. Once the struldbrugs hit 80 years old, they have "not only all the follies and infirmities of other old men" (3.10.13), but they are also extra-opinionated and cranky because they're worried about living forever.
Thus, the struldbrugs provide a satire of both old age and the dream of living forever. Gulliver's description of their decayed physical condition is pretty horrible, but their bodies aren't even the worst problems the struldbrugs face. The problems with living forever as an old person include:
- The marriages never last – in fact, by law, they get dissolved automatically at 80 – because no two people could stand each other for eternity.
- According to the law of Luggnagg, the struldbrugs become legally dead at 80 and can no longer hold their own property. This is to stop them from taking over the world and holding it forever (3.10.22). But in practice, it also means that the struldbrugs have to beg for all time.
- Language changes all the time. So, struldbrugs over the age of 200 generally can't understand the words of the younger generation, or even of younger struldbrugs.
In Jonathan Swift's novel Gulliver's Travels, the name struldbrug is given to those humans in the nation of Luggnagg who are born seemingly normal, but are in fact immortal. However, although struldbrugs do not die, they do nonetheless continue aging. Swift's work depicts the evil of immortality without eternal youth.
They are easily recognized by a red dot above their left eyebrow. They are normal human beings until they reach the age of thirty, at which time they become dejected. Upon reaching the age of eighty they become legally dead, and suffer from many ailments including the loss of eyesight and the loss of hair.
Struldbrugs were forbidden to own property:
As soon as they have completed the term of eighty years, they are looked on as dead in law; their heirs immediately succeed to their estates; only a small pittance is reserved for their support; and the poor ones are maintained at the public charge. After that period, they are held incapable of any employment of trust or profit; they cannot purchase lands, or take leases; neither are they allowed to be witnesses in any cause, either civil or criminal or economic, not even for the decision of meers (metes) and bounds.
Otherwise, as avarice is the necessary consequence of old age, those immortals would in time become proprietors of the whole nation, and engross the civil power, which, for want of abilities to manage, must end in the ruin of the public.
Chinese Taoism placed the Island of the Immortals eastward from China, while Swift places the struldbrugs near Japan.
The term struldbrug has been used in science fiction, most prolifically by Larry Niven and Robert Silverberg, to describe supercentenarians.