Devil's advocate
The advocatus diaboli (Latin for Devil's advocate) is a former official position within the Catholic Church, the Promoter of the Faith: one who "argued against the canonization (sainthood) of a candidate to uncover any character flaws or misrepresentation of the evidence favoring canonization". In common parlance, the phrase "playing devil's advocate" describes a situation where someone, given a certain point of view, takes a position they do not necessarily agree with (or simply an alternative position from the accepted norm), for the sake of debate or to explore the thought further using valid reasoning that both disagrees with the subject at hand and proves their own point valid.