def potential_purviews(self, direction, mechanism, purviews=False):
        """Return all purviews that could belong to the |MIC|/|MIE|.

        Filters out trivially-reducible purviews.

        Args:
            direction (str): Either |CAUSE| or |EFFECT|.
            mechanism (tuple[int]): The mechanism of interest.

        Keyword Args:
            purviews (tuple[int]): Optional subset of purviews of interest.
        """
        system = self.system[direction]
        return [
            purview for purview in system.potential_purviews(
                direction, mechanism, purviews)
            if set(purview).issubset(self.purview_indices(direction))
        ]