The perspicuity (clarity) of Scripture is a very important teaching of Scripture itself. One helpful resource on this topic is Mark Thompson’s A Clear and Present Word. I appreciated this paragraph:
“The clarity of Scripture can be affirmed on the basis of Scripture’s own teaching. The biblical text can be approached with confidence by the believer who seeks to know God and his purposes. God has been good to us in giving us the Scripture that we have. Here, in this cradle as Luther would put it, you will find the Christ. What is more, God has given us resources to help us as we read: his Spirit who has never abandoned his word, the fuller context of the whole Bible, and a fellowship of readers not only in our own time but stretching back to the time when these words were first written. The struggle between light and darkness remains the context of all our reading of Scripture in the last days. Yet the confidence of the apostle Peter continues to be echoed at the beginning of this third millennium: ‘we have something more sure, the prophetic word, to which you will do well to pay attention as to a lamp shining in a dark place, until the day dawns and the morning star rises in your hearts’ (2 Pet. 1:19).