Some suggest that the Bible is not a rule book and should be read as a conversation between God and his people, but Christian confessions declare it “the only rule for life and faith” (Westminster Confession). Which is right?
In your question we can discern two different nuances of the word “rule.” The confessions capture the idea of a standard, norm, or measuring stick—something that lays out the way things are meant to be. In other words, Christians ought to evaluate, measure, and interpret the world according to the standard, the “rule” that we find in Scripture. But though Scripture is the Church’s “infallible rule,” this does not make Scripture a “rule book.” Although the Bible contains various rules, commandments, statutes, and precepts, it would be a mistake to separate those rules from the larger story of Israel, Jesus, and the church.
Indeed, there are many rules in the Bible that no longer reflect the part of the story we are living in (e.g., laws concerning ritual purity). It is not that these passages have nothing to say to us; they might, for example, have much to teach us about the character of God. But the way these inspired passages remain “profitable” to us, equipping us for every good work (2 Tim. 3:16) is not as straightforward rules, but as guiding moments in the story of redemption. We are called to faithfully continue the story in the places we are planted, drawing direction on what to do from biblical doctrines that give us the vision of who God is, what God is up to, and what we should be about.
This means that the Bible is not just a conversational document, but a covenantal document, making claims on the way we live together in God’s word. Its authority is found in the triune God to whom it testifies, whose true story it tells, who still speaks in its pages. To acknowledge it as our “rule” is to acknowledge it as the authoritative story of the world.
To acknowledge it as our “infallible” rule means that it will not fail in accomplishing God’s purposes: telling us the truth, convicting us, consoling us, and including us in God’s life and love, for his glory and the good of all creation. Thus, whenever we read the Scriptures publicly, we rightly say, “this is God’s Word” and “thanks be to God!”