Amid changing societal values, McCarthy delves into themes like enduring moral and logical principles, authenticity, kindness, and sincere reactions in an increasingly unpredictable and artificial world. These ideals shouldn't be confused with reckless indulgence, as exemplified by those who try excessively to appear "natural" and "open," such as Norine Blake. Her affair with Harald reflects the breakdown of his marriage, and her leftist politics and Margaret Mead-inspired naturalism disregard the dignity and feelings of others. Helena Davison, serving as McCarthy's voice, offers a short lecture when Norine seeks advice about her relationship with Harald, promoting the traditional virtues of politeness and gentleness. Proper etiquette should be upheld to protect dignity and emotions, even when personal desires pose a challenge.

On the other end of the spectrum are individuals who are excessively restrained, prudish, or overly courteous, making them easily intimidated and manipulated by others. They embody an outdated standard of gentility and convention that the positive aspects of modern roles are rendering obsolete. For instance, a young woman's doctor husband insists she be a "subject" in his breastfeeding campaign, preventing her from comforting her crying baby, as he attempts to regulate the baby's "schedule." In all these characters, the standard for behavior is anchored in identity, defining and maintaining a sense of self that neither imposes on others nor makes one inflexible and unable to adapt to change and necessity.

Characters who uphold this core find peace and clarity, while those who fail to maintain it or never had it encounter risk. The Group is much more than a cautionary tale about the dangers of overstepping one's boundaries. Instead, it highlights new boundaries or new territories that are now considered acceptable.

In McCarthy’s own words, The Group is a novel about the “history of the loss of faith in progress.” If the novel’s uniqueness resides in the close orchestration of nine women into one character, it is no less unique for the documentary tone by which the progressive ideas of the time are captured, especially as these contrast with the conservative backgrounds of wealth from which the women come.

The novel’s documentary flavor is heavy in long passages such as those describing a first sexual experience, the implanting of the diaphragm, and theories of breast-feeding. At other times, the McCarthy intellect asserts itself in lectures on the melancholia psychosis that afflicts Polly’s father and the political theories debated by two of Polly’s housemates: Schneider, a Trostskyite, and Scherbatyef, a Stalinist. Although McCarthy invests her characters with ideas, they are not all her ideas, nor is any one character her clear raisonneur. Rather, it is the Vassar education that provides the women with intellectual views which they do not necessarily understand fully but which they insist on applying to their lives.

The autobiographical nature of much of the novel created a sensation in 1963. McCarthy herself was the first of her group to be married. Like Kay she married a Harold (spelled in the novel with “a”) and also spent some time in psychiatric treatment. Like Lakey, she wore her hair in a black knot at the nape of her neck. Like Norine, she has expressed lack of faith in progress. Scholars have identified at least four of the group members as real-life graduates of 1933, as well as recognizable composites of other friends and acquaintances of McCarthy.