There is to be found a medieval legal insight, called “the Mixta,” that will help us, I believe, to understand more fully why and how the Church must always face up alertly and virtuously to the morally contentious—and often protractedly litigious—realms of “overlapping jurisdictions,” lest there be unjust usurpations and inordinate encroachments upon the freedom of the Church (“Libertas Ecclesiae”) and of the Faith. That is to say, there will always obtrusively exist those endangered realms of life that are to be found in the so-called “threshold areas” or in the ambiguous areas of the “in between”: between the pure realm of “the Spiritualia” and the comparably unambiguous realm of “the Temporalia.” For example, we distinguish respectively the sacred offering of the Sacrifice of the Mass, from the financed building of public roads and drainage. A religious procession on those secular roads, if permitted, would present an example of “the Mixta.” Papal Concordats have been one way down the years of establishing co-operation and the specific limits and permissions for the Church.
This mediating moral and legal reality and derivative concept were thus helpfully, yet quite compactly, expressed by one simple Latin word of “the Mixta.” It has constituted a convenient “kind of shorthand,” as it were. Moreover, the abiding cautionary advice “to beware of ‘the Mixta‘” remains a permanent challenge to the Catholic Church and to the integrity and trustworthiness of the Catholic Faith.