Moll's disposal of her children is just one of the many immoral, unsavory activities in which she engages throughout the book. It's patently obvious that she regards them as nothing more than an onerous burden she wants to get rid off as soon as possible. It's fair to say that Moll doesn't have much of a maternal instinct, but even so, her actions in this regard are particularly shocking.
From a literary perspective, however, Moll's heartless decision makes perfect sense, for Moll Flanders is intended to be a picaresque romp through the dark back alleys of London's criminal underworld. Our guided tour guide in this sordid journey is the book's title character, a woman who moves about from place to place in search of riches. To put it bluntly, such a journey would've been impossible for Moll to make with two kids in tow.
Besides, Moll's shameful abandonment of her children allows Defoe to show us straight away just what kind of character we're dealing with here. For Moll, children are an encumbrance, an impediment to riches. And if there's one thing we know about Moll, it's that she'll allow nothing to stand in her way when it comes to the acquisition of money, not even her own flesh and blood.
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