power, and so they actually went out as missionaries to these arab tribes who were coming in to mesopotamia and actually made alliances with them which very often were political alliances or economic alliances. and the third thing they did was they addressed the tribal arabs' sort of crisis of identity, of moving from nomadism to settled farmers in this very rich agricultural area. so those three things combined together that resulted in the split of the rural urban -- i mean the rural arab population between the shi'a and the sunnis. c-span: how do you keep track of all this? [laughter] >> guest: well, i study it every day. c-span: what's been -- i mean, how long have you studied this? >> guest: well, about 30 years. c-span: and what value did i have -- does it have when you go over there, when you're actually on the scene in iran or iraq? and have you been to jordan and syria? >> guest: oh, yes, i've been in all of those countries. you go with i think a real cultural sensitivity, and i have found that i have not had problems working in this area that so many people say, oh, you must have

. >> reporter: for iraq's christian community, which traces its roots as far back as ang sent mesopotamiait's a bitter prospect. the only real guarantee for its safetisy a secure and democratic iraq, for "religion & ethics newsweekly, i'm kate sealy in iraq. >>> we have a profile now of abraham bergeez a doctor, popular writer tcher and advocator of the idea that the practice of medicine is a calling. speaking to him -- >> reporter: abraham has all the credentials and degrees befitting a professor at stanford medical school but is best known and acclaimed for his writing. two best selling memoirs that opened a different kind of medical vocation. >> my desire to be a physician has a lot to do with that sense of medicine as a ministry of healing. not just a science. not just a science and art but also a calling. also a ministry. >> reporter: his goal is to have today's medical students aspire similarly to a calling as much as a career in medicine. to awaken a more bake curiosity as they sharpen their clinical acumen. these third year medical students were studying abnormalityies. >> have yo