After Moll marries the Linen-Draper, she realizes that he is not the wealthy, aristocratic man she originally believed him to be, but a poor merchant. When reflecting bitterly on how he fooled her, she metaphorically compares him to an “amphibious creature”:
I was not averse to a Tradesman, but then I would have a Tradesman forsooth, that was something of a Gentleman too; that when my Husband had a mind to carry me to the Court, or to the Play, he might become a Sword, and look as like a Gentleman, as another Man.
[…]
Well, at last I found this amphibious Creature, this Land-water-thing call’d, a Gentleman-Tradesman.
Moll comparing the Linen-Draper to a “Land-water thing” and “amphibious creature” communicates how successfully her husband is able to shift his identity to match his environment, deceiving people in the process. The phrase “gentleman-tradesman” is, of course, a contradiction—in England’s rigid social hierarchy, a gentleman is far above a tradesman and it is not actually possible for someone to be both.
The reason Moll is so angry with the Linen-Draper for his deception is that she married him in the hopes of finding financial stability, as marrying a wealthier man was one of the only options for poor women looking to live a comfortable life. Unfortunately, because of the Linen-Draper’s masquerade, at the end of their relationship Moll is left with less money than she had when she met him.
After the Gentleman ends his years-long affair with Moll, leaving her alone with their young child and no consistent source of income, Moll reflects bitterly on how she must return to a life of crime, using a metaphor in the process:
I was now a loose unguided Creature, and had no Help, no Assistance, no Guide for my Conduct: I knew what I aim’d at, and what I wanted, but knew nothing how to pursue the End by direct means; I wanted to be plac’d in a settled State of Living, and had I happen’d to meet with a sober good Husband, I should have been as faithful and true a Wife to him as Virtue it self could have form’d: If I had been otherwise, the Vice came in always at the Door of Necessity, not at the Door of Inclination.
In this subtle metaphor, Moll imagines her life as a building containing two doors: “the Door of Necessity and “the Door of Inclination.” The only reason she chooses to engage in “vice” (or criminal activity) is because it comes in through the first door—that of necessity. In other words, because she is a “loose unguided creature” with “no Help, no Assistance, no Guide” and no access to “a sober good Husband,” the only step she can take is to return to a life of crime. She does not have the privilege to choose moral means of earning an income and ends up resorting to thievery and prostitution once more.
After Moll marries the Banker, she experiences a respite from the chaos of poverty and crime, and uses a metaphor to describe her experience of newfound peace:
Now I seem’d landed in a safe Harbour, after the Stormy Voyage of Life past was at an end; and I began to be thankful for my Deliverance; I sat many an Hour by my self, and wept over the Remembrance of past Follies, and the dreadful Extravagances of a wicked Life, and sometimesI flatter’d my self that I had sincerely repented.
Here Moll compares her marriage to the Banker to “land[ing] in a safe harbour" that protects her from “the Stormy Voyage of Life past.” This metaphor communicates the depths of her gratitude for the financial stability and comfort with which her new marriage provides her.
It is notable that, whenever Moll has a moment of comfort and calm in the novel—including this one—she reflects on her “past follies” and “wicked Life.” Of course, these moments do not last for long—after the Banker dies, she is again left without financial stability and must turn to crime to survive once more. Here Defoe is highlighting how poverty forces people like Moll to act against their morals.
After Moll meets a drunk man at a fair, sleeps with him, and steals from him, she reflects bitterly on his character, alluding to the Bible, specifically Proverbs 7:22-23:
There is nothing so absurd, so surfeiting, so ridiculous as a Man heated by Wine in his Head, and a wicked Gust in his Inclination together […] His Vice tramples upon all that was in him that had any good in it, if any such thing there was; nay, his very Sense is blinded by its own Rage, and he acts Absurdities even in his View; such as Drinking more, when he is Drunk already.
[…]
These are the Men of whom Solomon says, they go like an Ox to the slaughter, till a Dart strikes through their Liver.
Here Moll is attempting to justify her thievery by describing how the drunk man himself was behaving improperly, writing that he was “heated by Wine in his head” and had “a wicked Gust in his Inclination.” Her allusion to Proverbs also suggests that he is responsible for being robbed as, in that particular proverb, the ox willingly heading to slaughter is a metaphor for a man willingly following a prostitute to her home and facing negative consequences. The drunk man, Moll is arguing, should have been more careful—he has no one to blame for his stolen items but himself.