Formal and material principles of theology
Formal principle and material principle are two categories in Christian theology to identify and distinguish the authoritative source of theology (formal principle) from the theology itself, especially the central doctrine of that theology (material principle), of a religion, religious movement, tradition, body, denomination, or organization. A formal principle tends to be texts or revered leaders of the religion, while a material principle, its central teaching. The identification and application of this pair of categories in theological thinking were believed by Paul Tillich to have originated in the 19th century. As early as 1845 the Protestant theologian and historian Philip Schaff discussed them in his The Principle of Protestantism. They were utilized by the Lutheran scholar, F.E. Mayer, in his The Religious Bodies of America in order to facilitate a comparative study of the faith and practice of Christian denominations in the United States. This is also treated in a theological pamphlet entitled, Gospel and Scripture by the Commission on Theology and Church Relations of the Lutheran Church—Missouri Synod.
F.E. Mayer's findings 
Eastern Orthodoxy 
Roman Catholicism 
- Formal Principle -- the Bible, Tradition, Reason, the Pope, and the Magisterium.
- Material Principle -- "Man's soul, since it comes directly from God, is good and strives for reunion with God, realized in the beatific vision of God. Man's body is subject to sin and is alienated from God. Therefore man must be progressively justified, i.e., be made just. This result is effected when through the sacraments man enters into the 'state of grace' and observes the commandments which the church ... by her 'divine commission,' imposes upon the 'faithful.'"
- Formal Principle in general—The Bible, the authority of the church, and reason. Specifically, for individuals of different churchmanship:
- Low Church—the Bible as the only source and the all sufficient norm of religious truth.
- High Church -- "doctrinal authority rested successively in Christ, in the teaching church, in the Scriptures, and in the councils." This is called the consensus fidelium ("agreement of the faithful").
- Broad Church—along with the Bible and the consensus fidelium is included "God's self-disclosure in the religious and moral development of the human race as a whole, in the religion of Israel, the person of Christ, and the life of His mystical body, the church."
- Material Principle:
- Paul Tillich, A History of Christian Thought from Its Judaic and Hellenistic Origins to Existentialism, Carl E. Braaten, ed., (New York: Simon & Schuster, 1967), 280
- Philip Schaff, The Principle of Protestantism as Related to the Present State of the Church, John W. Nevin, trans., (Chambersburg, PA: Publication Office of the German Reformed Church, 1845), 54-94.
- F.E. Mayer, The Religious Bodies of America, fourth edition, (Saint Louis: Concordia Publishing House, 1961), passim.
- Gospel and Scripture
- Mayer (1961), p. 11.
- Mayer (1961), p. 13. Cf. also, On the Incarnation 54:3, PG 25:192B.
- Mayer (1961), p. 40.
- Mayer (1961), p. 47.
- Mayer (1961), p. 144.
- Mayer (1961), p. 144–147.
- Mayer (1961), p. 276.
- Mayer (1961), pp. 276–277.
- Mayer (1961), p. 277.
- Mayer (1961), p. 201–203.
- Mayer (1961), p. 203.
- Mayer (1961), p. 207.
- Mayer (1961), p. 206.
- Mayer (1961), p. 289.