Are they merely a guideline? Something we refer back to when needing to define our faith? How much weight should they have when deciding on issues of life and morality?
Shack,
Christianity is God's revealed religion. God is ultimately, and infinitely wise, truthful, and rational. Thus, whatever He reveals is wise, truthful and rational. God does not reveal inconsistent or contradictory propositions.
That said, His revelation must be viewed and understood, not as a set of unrelated (albeit heartwarming) ideas. Rather, Scripture is one consistent whole, and therefore may be brought together into a "pattern of sound doctrine" or a system of truth; a confession.
Thus, when a particular confession is in line with the teaching of Scripture, it is the same as God's Word. Here's how the WCF puts it:
Chap. 1:VI. 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
Note, nothing is to be added to what Scripture explicitly says, or to what may be deduced from Scripture using good and necessary consequence: theology.
Confessions are a bulwark against error, an encouragement to piety, and are a lowest-common-denominator, from which the church may then grow into the fullness of Him Who fills all in all.
Without sound confessions, we are subject to every wind of doctrine, the trickiness of men and their craftiness.
Here's a contemporary example. The Federal Vision is interested in twisting Scripture to say certain irrational propositions, clearly contrary to sound biblical theology and the Reformed confessions: justification is perfected or completed "eschatologically", based (at least in part) on our good works.
The Confessions soundly condemn this sort of mishandling of Scripture, and therefore, we are spared the trouble of giving such drivel a second hearing. We need not be troubled by the shades of falsehood, but may confidently affirm the truth, and move on. See Hebrews 6 for an example of people who had to rediscover the basics, rather than progress. Confessions are a help to this good end.
Not sure that this answers all questions, but I think is a starting point.
Cheers,