{{Muggles' Guide to Harry Potter/Intermediate Spoiler}}
A popular theory for why Mrs. Figg is selected as guard for Harry, is that no one could detect their magical power because Arabella is, a Squib, has none, and Harry is underage and so theoretically can't do magic. Harry's being underage would, of course, be no bar to the detection of his use of magic once he purchases a wand, as is amply demonstrated when the Ministry for Magic warns him about the use of magic in [[Muggles' Guide to Harry Potter/Books/Chamber of Secrets/Chapter 2|''Harry Potter and the Chamber of Secrets'']]. Perhaps a better explanation is Dumbledore's sympathy for the non-magical. It is likely Dumbledore who managed to get [[Muggles' Guide to Harry Potter/Characters/Argus Filch|Argus Filch]] a job as caretaker of the castle at Hogwarts, a job which is one of the few in the Wizarding world of which he is capable; likewise, this watchman job is one suited to Mrs. Figg's lack of Magicalmagical ability. It is also likely true that once a Wizarding child is tested as non-magical, and therefore a Squib, he or she no longer falls under the purview of the Ministry of Magic, and so is no longer tracked by that Ministry. Arabella could thus be set to watch over Harry, and the Ministry would be none the wiser that anyone was taking any interest in him.
