why did the late arthur jarvis devote himself to the service of south africa?

You have to wait until chapter 24 for Jarvis to spell it out for you. Through his writings he conveys the sense of doing the right thing no matter what the cost. Jarrvis loves South Africa, he even embraces the very uphill challange of race relations. It is almost a paradox but racial strife defines South Africa. Check out this quote from the book; I really think it illustrates his passion,

"I do this not because I am courageous and honest, but because it is the only way to end the conflict of my deepest soul. I do it because I am no longer able to aspire to the highest with one part of myself, and to deny it with another. I do not wish to live like that, I would rather die than live like that."