The sufficiency of Scripture is the doctrine that the Bible contains the whole counsel of God concerning all things necessary for His glory, man's salvation, faith, and life — and that nothing at any time is to be added to it, whether by new revelations of the Spirit or traditions of men. ^[raw/en/wcf-ch01-s06.md]
The Confession opens this section: "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." ^[raw/en/wcf-ch01-s06.md]
This phrase, drawn from Paul's farewell in Acts 20:27, affirms that nothing essential has been withheld. 2 Timothy 3:16-17 provides the great proof text: "All scripture is given by inspiration of God... that the man of God may be perfect, throughly furnished unto all good works." The Greek artios (perfect) means complete, lacking nothing; exartizo (throughly furnished) means outfitted completely for the task.
The Confession forbids two kinds of addition. First, "new revelations of the Spirit" — targeting the Enthusiasts who claimed direct revelations beyond the written Word. The canon is closed; the Spirit's work today is to illuminate, not to add. As Calvin teaches, "The office of the Spirit is not to form new revelations but to seal on our minds the very doctrine which the gospel recommends." ^[raw/en/wcf-ch01-s06.md]
Second, "traditions of men" — targeting Rome, which had elevated unwritten tradition to equal authority with Scripture. The Reformation principle that Scripture alone (sola Scriptura) is the infallible rule of faith and life stands against both errors.
The Confession balances its affirmation of sufficiency with a "nevertheless": "the inward illumination of the Spirit of God [is] necessary for the saving understanding of such things as are revealed in the Word." Scripture is objectively sufficient; but the human heart, darkened by sin, cannot grasp it without the Spirit's illumination. The Spirit does not add new content; He opens our eyes to see what is already there. ^[raw/en/wcf-ch01-s06.md]
The Confession also acknowledges that "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." This distinguishes the substance of worship (fixed by Scripture) from the circumstances (ordered by wisdom under Scripture's general rules).
Francis Turretin identifies three categories: (1) things necessary for salvation, (2) things deduced by good and necessary consequence, (3) circumstances left to Christian prudence. The second category is vital — the Trinity is not stated in a single verse but deduced from the whole biblical witness.
The clarity-of-scripture ensures that what is sufficient is also accessible: the whole counsel of God is contained in a book the ordinary believer can understand. Together, sufficiency and clarity protect the church from both the tyranny of those who would add to the Word and the despair of those who think it incomplete. This doctrine is the basis of sola-scriptura: because Scripture is sufficient, nothing else is needed as a rule of faith.