It is unclear exactly where Sofia Lamb came from, though it is safe to assume that it was somewhere in the United Kingdom, as evident by her southeastern British accent. From an early age, Lamb was raised by her father. He was a physician, and was a firm believer in the utilitarian ideal of the greater good, which he referred to as "the triage imperative". Sofia Lamb adopted his philosophy and later followed in his footsteps, specializing in psychiatry at the University of Oxford. While living in Hiroshima, Japan during World War II, she worked as a missionary providing medical relief for the survivors of the Hiroshima bombing. Lamb survived the bombings, but learned that the long, dear friends she made in Hiroshima were killed. Lamb was appalled when she discovered the United States were using her own altruistic ideal of "the greater good" to justify the bombing, and this convinced her that the world was doomed to destroy itself. When Andrew Ryan invited her down to his utopia to provide counseling for the isolated populace, she welcomed the opportunity.

Once Dr. Lamb arrived in Rapture, she began spreading her altruistic ideals, hoping to enlighten the citizens through "the common good" and create a true utopia. Her unconventional techniques involved free therapy sessions for the poor citizens in Pauper's Drop, poker games in which she intentionally lost to spread wealth to those who needed it, and the creation of an artistic commune at her personal property in Dionysus Park. After the birth of her daughter, Eleanor Lamb, she made certain that Eleanor would be the perfect vessel to continue furthering her goals. Lamb described her physical participation in Eleanor's birth as being "minimized", to avoid any possible biases. She attempted to keep her daughter isolated from other children and privately tutored her, hoping to raise a genius-level intellect.

Andrew Ryan noticed Lamb's growing influence with the citizens of Rapture and began to regret bringing her in. Her ideology of altruism largely clashed with his own, and Ryan saw her as a corrupting influence in his paradise. He agreed to a series of public debates, hoping to defuse Sofia's support by showing the flaws in her reasoning. The topics of these debates ranged from religious rights to the very nature of reality. These debates did not have the effect Ryan hoped. Later, her followers even shaped a religion around her ideals, referring to themselves as "The Rapture Family" and treating her philosophical book Unity and Metamorphosis as a sacred text.