Sound doctrine also requires that we reckon with what is taught implicitly. That is, what may be deduced from Scripture by good and necessary consequence is equally authoritative with what is stated in black and white and so is therefore equally binding. Deduction of good and necessary consequence involves getting at the background of a text or the bringing together of texts from different parts of Scripture and asking what these texts together mean.
For a decade the Westminster Assembly of divines (i.e., theologians) met at Westminster Abbey in London (1643-1653) to produce a Scriptural doctrinal standard and church government. During that time the well-known Confession of Faith was drawn up to explicate the system of doctrine drawn from the text of Scripture itself. In the profound first chapter of the confession where the primacy of Scripture was trumpeted, the divines articulated an interpretive principle that protects the sound handling and understanding of God’s Word. In particular, we find the following:
6. The whole counsel of God concerning all things necessary for his own glory, man’s salvation, faith and life, is either expressly set down in Scripture, or by good and necessary consequence may be deduced from Scripture: unto which nothing at any time is to be added, whether by new revelations of the Spirit, or traditions of men. Nevertheless, we acknowledge the inward illumination of the Spirit of God to be necessary for the saving understanding of such things as are revealed in the Word: and that there are some circumstances concerning the worship of God, and government of the church, common to human actions and societies, which are to be ordered by the light of nature, and Christian prudence, according to the general rules of the Word, which are always to be observed.