What allows us to endure our darkest moments? What does it take to show resilience in the face of adversity? In this hour, TED speakers explore the outer limits of inner strength. 1) Explorer Ben Saunders is the first person to finish the perilous trek from the edge of Antarctica to the South Pole and back. He describes what he had to endure in order to survive the journey. 2) Humanitarian Zainab Salbi explains how life continues in the midst of war -- and how the ones who "keep life going" are women. (10:39) 3) Astronomer and cosmologist Lord Martin Rees asks whether our species will endure despite the many existential threats we face. 4) Following the White House sex scandal of the 1990s, Monica Lewinsky endured public shame and trauma. Now, she is speaking out about it as a way to help others in similar circumstances. Hear it Sunday at 9 am.