Tis text focuses on the discussion of whether the Christian religion promotes democracy and defense of civil liberties or not. It provides an example: the case of the struggle of the citizens of Porto against the bishop for the autonomy of their city, in the XV Century. And concludes two things: it was the religion that gave the people the legitimacy and strength to resist both the royal and the ecclesiastical centralism and that was the central government that encouraged the fght against bishop, considered the king power limiter.