In ethics, Rand argued for rational and ethical egoism (rational self-interest), as the guiding moral principle. She said the individual should "exist for his own sake, neither sacrificing himself to others nor sacrificing others to himself". She referred to egoism as "the virtue of selfishness" in her book of that title, in which she presented her solution to the is-ought problem by describing a meta-ethical theory that based morality in the needs of "man's survival "qua" man". She condemned ethical altruism as incompatible with the requirements of human life and happiness, and held that the initiation of force was evil and irrational, writing in "Atlas Shrugged" that "Force and mind are opposites."