The Underground Man's personality is conflicted. Earlier, he has claimed that an individual with consciousness can never have an identity. Here we see this claim played out. The narrator is incapable of expressing an idea with conviction. He must always question it, either from his own point of view or from someone else's.
Consciousness always questions itself and can never reach a stable position.
This chapter also contains a direct reference to Rousseau. Rousseau is often credited with inventing a language to describe the individual self in his Confessions. In that book, Rousseau attempted to set down his own self as accurately as possible so that others might judge him. Rousseau's Confessions clearly serve as a model for this novel. The Underground Man insists that when writing for others, one inadvertently lies out of vanity.