Earlier I posted this argument from John Owen (mediated by Richard Muller) on the authority of Scripture. I just realized today that the same argument works for the clarity of Scripture. And this time, we have Scripture itself to attest to the clarity of natural revelation. Romans 1:19-21 are incredibly important here:
19. What may be known about God is plain to them, because God has made it plain to them. 20 For since the creation of the world God’s invisible qualities-his eternal power and divine nature- have been clearly seen, being understood from what has been made, so that men are without excuse. 21. For although they knew God, they neither glorified him as God nor gave thanks to him, but their thinking became futile and their foolish hearts were darkened (emphasis added).
Notice two things about this passage. Firstly, creation reveals God clearly. No magisterium of scientists is necessary to understand God’s invisible qualities, namely, His eternal power and His divine nature, from what has been made. Secondly, the reason why so many people do not see it (and who therefore arrogantly claim that the problem is in the revelation, and NOT in them) is their sin. When they worship and serve the creature rather than the Creator, their foolish hearts become darkened, and they can no longer see the truth.
I will simply point out that if this is true of natural revelation, how much more is it true of special revelation! Natural revelation has a clarity that reveals the things which God intended it to reveal. Special revelation has a clarity that reveals the things which God intended for it to reveal. Why would natural revelation be clearer than special revelation, when special revelation was given for a much more specific reason? God would be stupid to make His special revelation less clear than His natural revelation. Therefore, Scripture is clear in itself, with the Holy Spirit making sure that God’s people understand it. We need no churchly magisterium to understand the Scriptures.
Furthermore, not all the differences among Protestants (which are usually exaggerated while Roman Catholic differences are minimized) can shake this foundation, since, if sin distorts our understanding of natural revelation, how much more would it distort special revelation! The fault of misinterpretation lies not in the fact that Scripture is inherently unclear, but in the fact that sinful people distort its teachings.