Fourteen years later I finally get round to watching the movie. This was only because I know something about the character. He's playing a programmed multiple. That's MK-Ultra for the curious and can be explored in the tag below.
I don't usually watch this kind of thing but Matt Damon is superb. His girlfriend puts in a great performance too. Guess i'll have to download the other three now.
Programmed multiples can be mind controlled to be professors, sex slaves and most curiously for those who drill down into the subject; Satanist High Priestesses but then you have to sniff around genetics to learn more on that, and most people have no time to explore reality.