The Early Church saw the need very quickly of deriving doctrinal formulations from Scripture by the method of good and necessary consequence, which, other than producing a list of verses that may be variously interpreted, is the only way of producing a doctrinal formulation or creed. One of the classic and most critical creeds of the early Church was the Nicene Creed. The critical terms used in the creed such as “homousias” to define the divine nature of Christ are not derived by a churchly magisterial fiat but by good and necessary consequence from the Scriptures. J.D. Kelly writes concerning the usage of such terms, “... it was everywhere taken for granted that, for any doctrine to win acceptance, it had first to establish scriptural basis. A striking illustration is the difficulty which champions of novel theological terms like houmoousias’ (‘of the same substance’)... experienced in getting these descriptions of the Son’s relationship to the Father, or of God’s eternal being, generally admitted. They had to meet the damning objection, advanced in conservative as well as heretical quarters, that they were not to be found in the Bible. In the end they could only quell oppositions by pointing out (Athanasius in one case and Gregory of Nazianzus in the other), the meaning they conveyed was exactly that of Holy Writ.” in Early Christian Doctrines (San Francisco: Harper Collins, 1978) pg. 46.
The term “Trinity” was not found in the Scriptures, but it is a theological correct term which describes the doctrine that may be derived from Scripture by good and necessary consequence. Gregory of Nyssa displays how the method of good and necessary consequences was used in relation to the doctrine of the immortality of the soul in drawing out the principles of Scripture.
“we are not entitled to such license, I mean that of affirming what we please; we make the Holy Scriptures the rule and the measure of every tenet; we necessarily fix our eyes upon that, and approve that alone which may be made to harmonize with the intention of those writings. We...we will adopt, as the guide of our reasoning, the Scripture, which lays it down as an axiom that there is no excellence in the soul which is not a property as well of the Divine nature.” –Gregory of Nyssa, Nicene and Post Nicene Fathers II V. 5, p. 439.
John Leith notes that: 'All theology is in some measure dependent on this method, as all theologians have known since the time Augustine reflected upon the theological task'. In De Doctrina Christiana Augustine emphasized that good and necessary consequences were necessary in the interpretation of Scripture. In Book Two he discusses the extent to which the Christian should make use of other aids (such as history, natural science, dialectics, and rhetoric) in interpreting Scripture and formulating Christian doctrine. Chapters 31-35 discuss logic or reasoning. “The science of reasoning,” writes Augustine, “is of very great service in searching into and unraveling all sorts of questions that come up in Scripture....” Augustine notes that logic is not a human invention but ordained of God. “[T]he validity of logical sequences is not a thing devised by men, but it is observed and noted by them that they may be able to learn and teach it; for it exists eternally in the reason of things, and has its origin with God.”
John Calvin taught that teaching “drawn from Scripture” was “wholly divine.” (Institutes IV.x.30). Turretin contended also that the perfection of Scripture implies only the exclusion of traditions, and that the doctrine of the perfection or sufficiency of Scripture includes “besides the express word of God, evident and necessary consequences are admissible in theology.”(Institutes I.xii.2;6-7,8). Reformed scholastics viewed Scripture doctrines in two ways: kata lexin,
expressly, or kata dianoian, implicitly and as to the sense. Systematic theology or the formulation of doctrine depends upon this. BB Warfield noted that “the plea against the use of human logic in determining doctrine...destroys at once our confidence in all doctrines, no one of which is ascertained or formulated without the aid of human logic.” In the introduction to his Dogmatic Theology William G. T. Shedd stated that “the proper mode of discussing any single theological topic” is twofold: Exegetical and Rational. “The first step to be taken is, to deduce the doctrine itself from Scripture by careful exegesis; and the second step is, to justify and defend this exegetical result upon grounds of reason.” “When the individual doctrines have been deduced, constructed, and defended by the exegetico-rational method, they are then to be systematized.”
John Gill defended this theological method also in his Body of Doctrinal and Practical Divinity. “Systematical Divinity, I am sensible, is now become very unpopular. Formulas and articles of faith, creeds, confessions, catechisms, and summaries of divine truths, are greatly decried in our age; and yet, what art or science so ever but has been reduced to a system?” “Nor is every doctrine of the Scripture expressed in so many words; as the doctrine of the Trinity of persons in the Godhead; the eternal generation of the Son of God, his incarnation and satisfaction, &c. but then the things signified by them are clear and plain; and there are terms and phrases answerable to them; or they are to be deduced from thence by just and necessary consequences”.
Creeds and Confessions are necessary for the defence of the faith, instruction in the faith and making public confession of it. I Corinthians 2:10 commands believers that they all "speak the same thing." In Matthew 10:32 Christ says: "Whosoever therefore shall confess me before men, him will I confess also before my Father which is in heaven." How can we confess the divinity of Christ without good and necessary consequences? “No Creed but Christ” cannot have anything much to say about Christ at all. Thomas Boston notes 'The great fundamental article, that Jesus of Nazareth is the Messiah, before the New Testament was written, could not be proved to the Jews by express scripture testimony, but by good and necessary consequence; yet Christ tells them that there could be no salvation for them without the belief of this. 'If ye believe not that I am he (the Messiah),' says he, 'ye shall die in your sins.' John viii. 24'.
Christ promised the illumination of the Spirit to help the Church draw the principles of Scripture forth John 16:13: "Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will show you things to come." We are to give an answer or defence of the truth which will involve reasoning from the Scriptures (I Peter 3:15).
II Timothy 3:16, 17, "All Scripture is given by inspiration of God, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness: that the man of God may be perfect, thoroughly furnished unto all good works." Scripture is profitable for doctrine but we cannot have the teaching of it and the application of it let alone the systematising of doctrine without good and necessary consequence. Preaching and teaching encourages believers like the Bereans to search the Scriptures to see if the things taught in them are true (Acts 17:11). Paul did more than read the Scriptures, he reasoned from them in a way which could be confirmed by private examination of Scripture. 1 John 4.1 warns: ‘Beloved, do not believe every spirit, but test the spirits to see whether they be of God’ - this requires reasoning from Scripture. Bannerman, in his second volume on the Church of Christ shows how heretics or those in error have always insisted on explicit statements in Scripture rather than the inferences that may be drawn from them. “Errors are covered by an appeal to the letter of Scripture, while the real sense and meaning of it have been evaded or denied.”
William Cunningham wrote:
It has been the generally received doctrine of orthodox divines, and it is in entire accordance with reason and common sense, that we are bound to receive as true, on God’s authority, not only what is “expressly set down in Scripture,” but also what, “by good and necessary consequence, may be deduced from Scripture”; and heretics, in every age and of every class, have, even when they made a profession of receiving what is expressly set down in Scripture, shown the greatest aversion to what are sometimes called Scripture consequences,- that is, inferences or deductions from scriptural statements, beyond what is expressly contained in the mere words of Scripture, as they stand in the page of the sacred record.
B. B. Warfield noted that the method of good and necessary consequences 'is the strenuous and universal contention of the Reformed theology against the Socinians and Arminians, who desired to confine the authority of Scripture to its literal asservations; and it involves a characteristic honoring of reason as the instrument for the ascertainment of truth. We must depend upon our human faculties to ascertain what Scripture says; we cannot suddenly abnegate them and refuse their guidance in determining what Scripture means. This is not, of course, to make reason the ground of the authority of inferred doctrines and duties. Reason is the instrument of discovery of all doctrines and duties, whether ‘expressly set down in Scripture’ or ‘by good and necessary consequence deduced from Scripture’: but their authority, when once discovered, is derived from God, who reveals them and prescribes them in Scripture, either by literal assertion or by necessary implication.
It is the Reformed contention, reflected here by the Confession, that the sense of Scripture is Scripture, and that men are bound by its whole sense in all its implications. The re-emergence in recent controversies of the plea that the authority of Scripture is to be confined to its expressed declarations, and that human logic is not to be trusted in divine things, is, therefore, a direct denial of a fundamental position of Reformed theology, explicitly affirmed in the Confession, as well as an abnegation of fundamental reason, which would not only render thinking in a system impossible, but would logically involve the denial of the authority of all doctrine of the Trinity, and would logically involve the denial of all doctrine whatsoever, since no single doctrine of whatever implicitly can be ascertained from Scripture except by the process of the understanding. It is, therefore, an unimportant incident that the recent plea against the use of human logic in determining doctrine has been most sharply put forward in order to justify the rejection of a doctrine which is explicitly taught, and that repeatedly of a doctrine which is explicitly, in the very letter of Scripture; if the plea is valid at all, it destroys at once our confidence in all doctrines, no one of which is ascertained or formulated without the aid of human logic'.