"Good. So those are our tactics—to tell no one about the baby, not even Miss Abbott."
"Most certainly this is the proper course," said Mrs. Herriton, preferring "course" to "tactics" for Harriet's sake. (5.25)
The Herritons like to believe that they're respectable, honorable members of society, but in reality, they only want to appear to be respectable, honorable members of society. Keeping up appearances is the most important rule in the Herriton household. Their hypocritical behavior is emphasized by the fact that Mrs. Herriton uses the word "course" instead of "tactics," a sign that she's trying to make her actions appear more ethical than they actually are.
"I hated the idleness, the stupidity, the respectability, the petty unselfishness. [...] I had got an idea that every one here spent their lives in making little sacrifices for objects they didn't care for, to please people they didn't love; that they never learnt to be sincere—and, what's as bad, never learnt how to enjoy themselves." (5.64)
Miss Abbott's outpouring in this scene sums up in a nutshell exactly what Forster is criticizing about the hypocrisy of English society: the "petty unselfishness". It's important that Caroline doesn't say petty selfishness. This is the root of English hypocrisy: people like to act as if they're being unselfish, but in truth, they're being petty, insincere and completely self-serving.
He saw that his mother was not sincere. Her insincerity to others had amused him, but it was disheartening when used against himself. (5.146)
Philip experiences the full force of his mother's hypocrisy when Mrs. Herriton decides that he must go to Italy to retrieve the baby. Philip knows that his mother would much rather pretend as if the baby had never been born, but she's so overly concerned about what other people think of her, that she would go so far as to adopt the child just to keep tongues from wagging.
In one moment an impenetrable barrier had been erected between them. They were no longer in smiling confidence. Mrs. Herriton was off on tactics of her own—tactics which might be beyond or beneath him. (5.147)
The fact that Mrs. Herriton goes from hiding the existence of Lilia's baby to suddenly wanting to adopt the child shows the extent of her hypocrisy. The only reason she changed her mind is to keep people from gossiping about her. The narrator's use of the word "tactics" further emphasizes that Mrs. Herriton is willing to cook up any scheme that will ensure the protection of her reputation.
She could not bear to seem less charitable than others. (5.157)
The key word in this sentence is "seem." Mrs. Herriton doesn't mind being uncharitable behind closed doors (after all, she wasn't very nice to Lilia), but in the public eye, she is careful not to give anyone a chance to say a single bad word against her.
"I am planning what can be done," she would tell people, "and that kind Caroline Abbott is helping me. It is no business of either of us, but we are getting to feel that the baby must not be left entirely to that horrible man. It would be unfair to little Irma; after all, he is her half-brother." (5.158)
We can't help rolling our eyes at Mrs. Herriton's effortless ability to tell lies. It's so obvious that she wishes Lilia never had a baby in the first place. But in front of people, Mrs. Herriton plays the role of the concerned, lovely grandmother who only wants to do what's best for the poor child. Lies, all lies!
"What do you think of it?" she asked her son. "It would not do to let him know that we are anxious for it." (5.161)
In this scene, Mrs. Herriton asks Philip what he thinks of the letter she wrote to Gino offering to adopt the baby and finance his upbringing and education. What is she implying when she says "it would not do" for Gino to know their full intentions for the child? Clearly, Mrs. Herriton is up to her usual no-good scheming—she doesn't want Gino to realize how much they want the child in order to keep him from asking for too much money. But she doesn't even realize how hypocritical she's being: she thinks that the "right" thing to do here is to provide the baby with a proper English upbringing, yet how is it morally right to separate a father from his son?
She must be professing one thing and aiming at another. What the other thing could be he did not
stop to consider. Insincerity was becoming his stock explanation for anything unfamiliar, whether that thing was a kindly action or a high ideal. (5.177)
Philip is puzzled by Miss Abbott's actions—he can't tell whether she sincerely wants to help the child or if she only feels guilty for being involved in Lilia's unfortunate marriage. The fact that insincerity is now Philip's "stock explanation" for anything he doesn't understand shows just how cynical he has become.
"What about the baby, pray? You've said a lot of smart things and whittled away morality and religion and I don't know what; but what about the baby? You think me a fool, but I've been noticing you all today, and you haven't mentioned the baby once. You haven't thought about it, even. You don't care. Philip! I shall not speak to you. You are intolerable." (6.46)
Miss Abbott criticizes Philip here for his apathy and insincerity. Like his mother, Philip doesn't care about the baby at all, but he puts on an act to pretend as if he's concerned about the child's welfare. Does Philip believe what he says, or is he all talk and no action?
"Your mother has behaved dishonourably all through. She never wanted the child; no harm in that; but she is too proud to let it come to me. She has done all she could to wreck things; she did not tell you everything; she has told Harriet nothing at all; she has lied or acted lies everywhere. I cannot trust your mother. (6.112)
Miss Abbott can see right through Mrs. Herriton's lies and double-crossings. Is Mrs. Herriton a wicked person, or is she the product of a hypocritical society? Is Miss Abbott behaving more honorably than Mrs. Herriton, or are her motives just as morally questionable?
"He doesn't try to keep up appearances as we do." (10.7)
Miss Abbott admires Gino for his honesty, even when it comes off as too blunt or vulgar. Unlike the Herritons (and English society, more generally), Gino doesn't try to "keep up appearance." He says what's on his mind without regard to whether it's "proper" or "mannerly." The Herritons would be appalled by what they see as his unconventional, uncivilized behavior, but Miss Abbott likes Gino's sincerity.
"She will soon be her old self," was the reply. For Harriet, after a short paroxysm of illness and remorse, was quickly returning to her normal state. She had been "thoroughly upset" as she phrased it, but she soon ceased to realize that anything was wrong beyond the death of a poor little child. Already she spoke of "this unlucky accident," and "the mysterious frustration of one's attempts to make things better." (10.28)
Harriet is really no better than her mother when it comes to justifying her actions as morally correct. Even though Harriet is the direct cause of the baby's tragic death, she soon excuses herself from any moral responsibility or guilt by thinking of the event as merely a "tragic accident."