The term collectivism refers to the belief that an individual is part of a larger group, such as a family or an ethnic group. Collectivists believe that surviving life requires protecting the needs and desires of the group, not just the individual. Only through placing value on the group can an individual's own needs and desires be fulfilled. Finally, it should also be noted that members of a group with a collectivist mindset are very "close psychologically and emotionally" among themselves but "distant toward nongroup members" (University of the Pacific, "Individualist or Collectivist"). Collectivism stands in contrast with individualism, which is the belief that "the individual identifies primarily with self, with the needs of the individual being satisfied before those of the group" ("Individualist or Collectivist").
Toni Morrison's novel Sula is ultimately about the destruction of a tight-knit community in Medallion, Ohio, and, therefore, ultimately about the destruction of collectivism. However, the friendship between Sula and Nel can be considered a collectivist friendship, at least for a time, and Nel lives her life with a collectivist mindset, despite the fact that Sula lives as an individualist.
Morrison explains early in the novel that Sula and Nel's friendship was formed speedily and strongly because they felt they shared a common bond in the fact that they were both oppressed black girls who would grow up to be oppressed black women. The narrator phrases the point in the following:
Because each had discovered years before tat they were neither white nor male, and that all freedom and triumph was forbidden to them, they had set about creating something else to be. ("1920")
What they set out to be was black women among the community of black women. Furthermore, when they met each other, they set out to form their own community of two black women who leaned on each other for support.
However, Sula and Nel grew apart when Nel married Jude Greene and formed a new community for herself that she could look after with a collectivist mindset. In her collectivist mindset, everything she does is for the sake of Jude's happiness and for the sake of caring for her three children. In contrast, everything Sula does is for her own self-satisfaction, which even includes robbing Nel of her husband.