Ayn Rand originally envisioned Atlas Shrugged as a socio-political novel that would build on the ethical ideas of The Fountainhead. But as she worked on Atlas, she developed and revised her ethical thought in unexpected ways. This lecture explores how, and why, her ideas changed—as well as what did not change. Topics include life as an ultimate value; the relation between life and happiness; the relation between spiritual and material values; the importance of asking why morality is needed; the idea that morality presupposes a basic choice to live; and the question of whether rationality or independence is the primary moral virtue. Special attention will go to the pivotal role of The Moral Basis of Individualism, the nonfiction work Rand began shortly after the publication of The Fountainhead (but later set aside). The lecture assumes familiarity with The Fountainhead and Atlas Shrugged but presupposes no further background.