Warfield on the Need to Obey both the Explicit and Implied in Scriptural Teaching

Men are required to believe and obey not only what is "expressly set down in Scripture," but also what "by good and necessary consequence may be deduced from Scripture."  This is the strenuous and universal contention of the Reformed theology against Socinians and Arminians, who desired to confine the authority of Scripture to its literal asseverations; and  it involves a characteristic honoring of reason as the instrument for the ascertainment of truth.  We must depend on 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 and prescribes them in Scripture, either by literal assertion or by necessary implication.  The Confession is only  zealous, as it declares that only Scripture is the authoritative rule of faith and practice, so to declare that the whole of Scripture is authoritative, in the whole stretch of its involved meaning.  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 reemergence in recent controversies of the plea that the authority of Scripture is to be confined to its express 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 the abnegation of fundamental reason, which would not only render thinking in a system impossible, but would discredit at a stroke many of the fundamentals of the faith, such e.g. as the doctrine of the Trinity, and would logically involve the denial of the authority of all doctrine whatsoever, since no single doctrine of whatever simplicity can be ascertained from Scripture except by the use of the processes of the understanding (B. B. Warfield, "The Westminster Doctrine of Holy Scripture" in The Works of Benjamin B. Warfield, Volume VI: The Westminster Assembly and Its Work, 226-27).