1. “Theology” in the most general sense means thought and talk about God. Theology is also about ourselves and everything else, considered in relation to God. Philosophical theology (sometimes called “natural theology” or “theodicy”) is distinct from sacred theology. The former proceeds by the light of reason, while the latter proceeds by the light of faith and uses reason only as a tool of faith (see S.t., 1, q. 1, a. 1; a. 5, ad 2; a. 8, ad 2; S.c.g., 1, 9).
2. Sometimes the word “theology” is used to refer to the systematic features of a scriptural author’s appropriation (that is, personal reception) of divine revelation: We speak of the “theologies” of St. Paul, of St. John, and so on. It should not be supposed, however, that Scripture and our reflections on faith are theology in the same sense. Since it was essential to the completion of God’s act of communication that revelation be personally received and made their own by persons whom God chose for that purpose, the Scriptures, together with sacred tradition, constitute the supreme rule of faith (see DV 21). We receive Christian faith only by understanding and using the books of the Bible as the Catholic Church understands and uses them in her teaching, liturgy, and life. Hence, the “theologies” in Scripture itself are normative—that is, they set the standard—for our reflections on faith.
The books of the New Testament in particular bear perpetual and divine witness to the effective communication accomplished by the revelation of God in the Lord Jesus (see DV 17). Inasmuch as these books were written by the apostles and their associates, they reflect apostolic belief and teaching, which contains the basic appropriation of the words and deeds of Jesus and the authorized witness to his resurrection (see DV 7–8, 18, 20; LG 18–19).
We cannot rightly read the books of the New Testament if we imagine that they contain mere interpretations of an ineffable “revelation.” Revelation is communication, and the communication was not accomplished until what Jesus said and did was appropriated by the apostles under the inspiration of the Holy Spirit (cf. Jn 14.26; 15.26–27; 16.13).2 Therefore, we have no more direct access to God’s revelation in Jesus than the New Testament writings, understood and used as the Catholic Church understands and uses them in her teaching, liturgy, and life. It follows that, for our own thinking and speaking about matters of faith and morals, we ought to regard the various theologies of the New Testament as compatible, mutually complementary, and each a genuine constituent of the supreme rule of faith.
3. In a narrower sense, “theology” refers to reflection upon the sources in which the truth of faith is articulated. Such theology is subordinate both to Scripture and to certain other documents which bear witness to the faith of the Church. Among these latter, the documents of the general councils, such as Trent, Vatican I, and Vatican II, have a special place. The present work is theology in this narrower sense. It proceeds in the light of faith, with constant reference to Scripture and other authoritative expressions of the Church’s faith.
4. “Interpretation” in a technical sense refers to the spontaneous appropriation of a communication; thus, the inspired writers are said to have interpreted God’s message. In the ordinary sense, however, “interpretation” refers to systematic efforts to facilitate communication and overcome misunderstandings. This is where theology as we commonly understand it begins. The theological interpreter tries to find and state the true and full meaning of texts of Scripture and other authoritative expressions of the Church’s faith. This is the task of the part of theology called “positive theology.”
5. Although the study of Scripture is positive theology’s most important work, other witnesses to faith must also be studied. This is so because sacred tradition is essential to the handing on of God’s word, and the magisterium (living teaching office) of the Church has the unique role of proclaiming this word authoritatively to each generation (see DV 9–10). Moreover, all that the Church is belongs somehow to the tradition of revelation and so to faith (see DV 8). The positive theologian, therefore, studies not only documents, such as those containing the Church’s teaching, but also the history of the Church, the lives of the saints, the liturgy, and so forth. The purpose is to help people hear and accept God’s revelation in all its richness (see DV 23–24; OT 16).
A very important part of the work of positive Catholic theology is to locate the origin of the Church’s beliefs in the books of sacred Scripture and in other witnesses, and trace their development up to the present. Part of this task is to show how doctrines defined by the Church, understood in the precise sense in which the Church understands them, already are in some way present in Scripture and tradition, and to show this without reading into these sources anything which cannot be found there (see DS 3886/2314).
6. The method of positive theology is primarily linguistic-literary and historical. A theoretical framework is necessary for this discipline, as for any scholarly study. For Catholic positive theology, however, this framework ought not to be a construct of theories from outside revelation but should be the theoretical framework provided by developed Catholic teaching. This teaching is not extrinsic to revelation, but rather transmits it intact (see DV 10).3
7. Besides positive theology, Catholic theology also includes systematic reflection. Systematic theologians try to determine the relationships between truths of faith and other propositions which are not revealed but seem true. The goal is fuller understanding of the truths of faith and their implications. A classic formula summing up the work of systematic theology is “faith seeking understanding” (see S.c.g., 1, 8).
St. Cyril of Alexandria, commenting on John 6.70, beautifully expresses the common Christian conviction that faith is intellectually dynamic: “. . . knowledge comes after faith and not before it, according to what is written: ‘If you have not believed, neither have you understood [Is 7.9 in the Septuagint].’ When we have first within us a kind of basis for the augmentation of faith, then knowledge is built up little by little, and we are restored to the measure of stature in Christ and are made a perfect man and spiritual [cf. Eph 4.13]” (FEF 2111; cf. St. Augustine, FEF 1429, 1486, 1499, 1826). On this view, growth in understanding of what is of faith, which systematic theology attempts to promote, is not an optional extra for Christians, but an essential aspect of Christian life.
8. The following consideration helps to clarify the role and importance of systematic theology. God reveals himself in order to establish a personal relationship with us. Through this relationship he wishes to bring humankind, and indeed all things, into personal touch with himself: “to unite all things in him [Christ], things in heaven and things on earth” (Eph 1.10). This is a work of integration in which we are called to play a significant part. But to integrate realities, we must know and act upon the truth about them (see S.t., 1, q. 1, a. 6). Truths of faith must be integrated with all other truths we can know. Systematic theology helps us do this and so helps us cooperate in the work of restoring all things to God through Christ.
Systematic theologians help the whole people of God to carry out this work of integration; they help especially at the boundary where revealed and nonrevealed truths meet. Here rational reflection upon nonrevealed truths extends to consider those truths which can be known by reason and which also pertain to revelation. The systematic theologian attempts to illuminate and guide rational reflection in order to inform it with the light of revelation, while attempting, in exchange, to borrow from reason enlightened by faith truths which will expand understanding of the truths of faith.
2. A good, general introduction to the theology of revelation: René Latourelle, S.J., Theology of Revelation (Cork: Mercier Press, 1966).
3. The Sacred Congregation for Catholic Education, The Theological Formation of Future Priests (Washington, D.C.: United States Catholic Conference, 1976), sections 30–33 (hereinafter cited as “CCE” with the relevant section numbers). Concerning the proper methods for the study of Scripture, see three encyclicals: Providentissimus Deus (Leo XIII), Spiritus Paraclitus (Benedict XV), and Divino Afflante Spiritu (Pius XII). These encyclicals received their indispensable complement from Vatican II’s constitution, Dei verbum, which at crucial points incorporates their doctrine by reference (see esp. DV 11–12). A balanced theological study of theological problems concerning Scripture: Pierre Grelot, The Bible Word of God: A Theological Introduction to the Study of Scripture, trans. Peter Nickels, O.F.M.Conv. (New York: Desclee, 1968).