What led the Roman Catholics astray was their understanding that the church birthed the Word of God, rather than the Word being the foundation of the church (Eph. 2:20). Yes, God gives us consciences, good sense, and even the traditions of the church from which we can glean insight into life, but knowledge of salvation is found in Scripture and Scripture alone.
When we talk about sola scriptura, we are talking about the fact that it is God’s word—not man’s—that gives us the instruction we need to attain everlasting life. It’s not to say that Christians should only read the Bible and nothing else. If your sink gets clogged, a plumbing manual will be of more use than anything in the Old or New Testament. Sola scriptura means that the Bible gives us everything we need to know about everything that truly matters—specifically, our salvation.
The Sufficiency of Scripture
At the time of the Reformation in the sixteenth century, the Roman Catholic Church did not deny the importance of the Word of God but rather its sufficiency. Rome said Scripture was insufficient to reveal to us the way to heaven. Rather, Rome argued that we needed something in addition to Scripture: the traditions of the church. According to theologian Michael Horton in The Christian Faith,
The Council of Trent [in the sixteenth century] established the view that Scripture and tradition are actually two forms of God’s Word—”written” and “unwritten”.” (p. 188)
What led the Roman Catholics astray was their understanding that the church birthed the Word of God, rather than the Word being the foundation of the church (Eph. 2:20). Yes, God gives us consciences, good sense, and even the traditions of the church from which we can glean insight into life, but knowledge of salvation is found in Scripture and Scripture alone.