Bergman builds The Seventh Seal around a pointed contrast the film never states outright but keeps returning to visually: the knight Antonius Block's tortured, argued, intellectualized doubt set directly against the simple, unreflective faith of Jof and Mia, a young couple of traveling performers he meets and eventually shields on the road. Jof reports visions, of the Virgin Mary teaching the infant Christ to walk, that he takes for granted as real without needing to defend them, a directness Block, who has spent years fighting a Crusade in God's name and returned only with more questions, cannot access no matter how hard he searches for it.
The film resists resolving the contrast in either direction. Jof and Mia's faith is not proven right by anything that happens to them; it survives simply because Block, in the one deliberate act he manages to perform against Death, arranges for them to be elsewhere when Death's dance finally comes for the rest of his traveling companions. Block gets no vision, no voice, no confirming sign of the kind Jof describes so easily, and dies still not knowing whether anyone was listening.
Critics and theologians have read the ending in sharply different ways ever since, some as a bleak confirmation of Block's doubt, others as a quiet argument that meaning survives even without metaphysical proof, through the specific, concrete act of protecting people one can actually reach. Bergman himself declined for decades to settle which reading he intended, treating the ambiguity as the honest position rather than a gap to be closed.