Daughter of Destiny
I just finished reading Daughter of Destiny. It's a powerful story of how evil can be challenged by people who are willing to risk their lives for what they believe in. Benazir Bhutto was imprisoned or detained for 7 years but never wavered in her belief that what she was doing was right for her country. One paragrahp in particular haunted me (at the beginning of chapter 6) where she talked about the meaning of "I think, therefore I am." She says, "I am having more difficulty with it as the empty hours of detention drag on. I think even when I don't want to, but as the days slowly pass, I am not sure whether I exist at all. To truly exist, a person must effect something, act and cause a reaction. I feel that I have nothing on which to leave an imprint."
The meaning of existence for her is to have an impact. And, of course, if that impact is positive for others, a person can effect amazing change.