Science […] has granted us the gifts of life, health, wealth, knowledge, and freedom documented in the chapters on progress. To take just one example from chapter 6, scientific knowledge eradicated smallpox, a painful and disfiguring disease which killed 300 million people in the 20th century alone. In case anyone has skimmed over this feat of moral greatness, let me say it again: scientific knowledge eradicated smallpox, a painful and disfiguring disease which killed 300 million people in the 20th century alone.