It’s a classic thesis of Christian theology — especially dear to the Reformed tradition, but with appeal more broadly — that Christ fulfills a threefold office in his temporal mission, of prophet, priest, and king. Jesus sums up the three principal offices of canonical Israel, prophetically calling the LORD’s people to repentance, expiating sins as Israel’s true priest, and delivers Israel as her true king. We can also map this threefold office onto the three dominant explanations of Christ’s atoning work on the cross. Christ’s prophetic office corresponds to the “moral influence” theory, associated especially with Abelard (though its substance is already articulated by Augustine in De Trin. 4) — as the true prophet, Christ offers a stunning display of charity that moves the hearts of his people to follow him. Christ’s priestly office corresponds to the “satisfaction theory” of atonement, associated especially with Anselm (though again, present all over the tradition, in Athanasius for instance) — as the true priest, Christ offers himself as a “gift exceeding every debt” (so David Hart summarizes Anselm). And Christ’s kingly office corresponds to the “Christus Victor” theory of the atonement, according to which Christ conquers the powers of Sin and Death that hold the cosmos in bondage.
In his 1873 preface to a new edition of his Prophetical Office of the Church, Newman argues that the Church, as Christ’s body, participates in this threefold office. He criticizes his Anglican self for focusing exclusively on the Church’s prophetic office, to the neglect of its kingly and priestly vocations. Each of these vocations, he argues, serves a distinct purposes, and manifests itself in distinct institutions, each of which can find itself in tension or even prima facie conflict with the others. So, the prophetical office of the Church aims at theological truth, and historically is carried, Newman argues, in the various theological schools (whether in universities or monastic orders), which act as a critical brake on devotional or political excess. The priestly office of the Church yields popular religious devotion — the artless and impassioned piety, so often manifest among Catholics in an excessive cult of the saints, which is the spiritual love language of the great unwashed. And the kingly office of the Church yields the ecclesial hierarchy, centered in the Apostolic College of bishops whose head is the pope. The play of forces generated by these three offices, Newman argues, is a source of strife and of creativity in the life of the Church.