Dr . Steven Pinker on Are we really born a blank slate? Dr. Pinker uses his book - "The Blank Slate" - to explore the idea of human nature and its moral, emotional, and political colorings Part 2 - lectures- Dr. Leon Kass, Chair of the President's Council on Bioethics, examines the distinct ethical dilemmas that surround stem cell research. Dr. Kass will address a fundamental philosophical question underlying these latest scientific advances: Why not immortality?