Walking Through Westminster, WCF 1.6

Westminster Confession of Faith 1.6

"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."

Summary

Everything that we need to know for faith and life in God is either explicitly set down for us in the Bible, or is deduced from what the Bible does say by good and necessary consequence. For example, while the Bible never says anything about pornography, we can still rightly say that pornography is condemned by Scripture because of what the Bible does say about lust and adultery. Nothing may ever be added to or taken from what God has already said, even if someone claims a new revelation of the Spirit or a tradition of even the Church herself. 

This does not mean that everything that we could know about God is in the Bible; no amount of books could contain everything that could be known of God, since He is infinite (John 21:25). What this means is that the Bible contains everything we need to know about God to be saved and to live a joyful, obedient life. But, as stated in section V, only by the illumination of the Spirit of God do these things become revealed from the Bible. 

There are some issues that are not directly addressed in Scripture that are open to variation, specifically things related to the worship of God and church government. For example, while the Bible commands the Presbyterian form of church government, with elders and deacons appointed in every local church, there is no particular command on the number of elders and deacons. This varies from congregation to congregation, but should still be done in accordance with what is clearly revealed. Another example would be psalm-singing. The Bible clearly commands us to sing the psalms (Eph 5:19). However, there are no specifics on how that is to be done. Should a congregation sing straight through the psalter? Should they skip around and choose different psalms every week, depending on the sermon, etc? Should a particular psalm be sung to a certain tune? These questions are not directly spelled out in the Bible, and are open to variation, provided that all is done within the confines of what the Bible does say.