When we were walking through the narrow alleys [of the Mathare Valley slums], it was literally impossible not to step in the raw sewage and the garbage alongside the little homes. But at the same time it was also impossible not to see the human vitality, the aspiration and the ambition of the people who live there.

I'm relentless in that I deeply believe in people.

1.5 billion people lack proper access to electricity. Many buy kerosene, which can cost 30 percent of their income. It sends millions of metric tons of carbon dioxide into the atmosphere every year. And often the lamp will fall over and catch the house on fire. So mothers hate it, but it's their only option.

Africa can stun you in an instant. It can throw floods and drought and disease at you, sometimes all at the same time. In the next moment, it will tease you with its magnificent beauty, so even if you don't forget, you can find a way to forgive. Ultimately, it keeps you coming back for more.

Human beings tend not to spend money on health preventionally. We tend to spend it on top treatment.

The human spirit is extraordinary. If we give the 3 billion people who live in poverty the opportunity to change their lives, they will. For too long, we've looked at needing to "save" these people - with an emphasis on "these people" - rather than removing the constraints keeping them from solving their own problems.

When we deny the poor and the vulnerable their own human dignity and capacity for freedom and choice, it becomes self-denial. It becomes a denial of both our collective and individual dignity, at all levels of society.