When the Interplanetary Security and Intelligence Agency discover an ancient underground city on a newly found extra-solar planet, they investigate potential candidates to lead the top-secret mission.
William is chosen because of his excellent standing in school, and because of the fact that he virtually has no close relationships with anyone, as well as having no connections to a particular religious belief. The ISIA believes that because of that, there will be no bias as to what they find. The existence of previous life would have no impact on any previous beliefs.
William is a man of science, believing that because of the sheer vastness of space, the probability of life being out there somewhere is high. However, the fact that his field isn't astronomically based adds to the unbiased personality that the agency is looking for.