The narrator makes frequent use of verbal irony, both for humor and as a way of criticizing unjust people and institutions. A good example of the narrator's verbal irony is in Chapter 2, when the narrator describes the woman who is charged with caring for Oliver and other orphaned children in the parish:
Sevenpence-halfpenny’s worth per week is a good round diet for a child; a great deal may be got for sevenpence-halfpenny—quite enough to overload its stomach, and make it uncomfortable. The elderly female was a woman of wisdom and experience; she knew what was good for children, and she had a very accurate perception of what was good for herself. So, she appropriated the greater part of the weekly stipend to her own use, [...] proving herself a very great experimental philosopher.
This passage seems at first to have a logical structure and tone. It congratulates the woman, Mrs. Mann, on her choice to keep most of the money the state provides for the children. Although the passage literally praises Mrs. Mann, though, its real meaning is the opposite: it is a biting criticism of her choice to profit off of orphans by starving them. The narrator leaves a couple of clues for the reader that this commentary is sarcastic.
In addition to the implausibility of the idea that the state is overfeeding orphans, the narrator also uses deliberately bad logic. The decision not to feed the children much is supposedly "proof" that Mrs. Mann is an "experimental philosopher," but her decision is not based on any kind of thought experimentation at all. On the contrary, she goes into the decision with her mind made up about what is best for everyone (especially her) and acts in her own best interest. It is flat-out wrong to claim that this decision proves her an experimental philosopher. What's more, many Victorian readers would have found it amusingly incongruous to imagine a woman who takes care of orphans as an intellectual figure. The passage invites the reader to trip up on its bad logic and absurdity, ultimately coming to criticize Mrs. Mann for pretending that there is a good reason for her selfishness.