Perspicuity of Scripture
Protestants, in defense of their belief that every Christian can interpret the Bible for himself, claim that this is possible because the Scriptures are clear (perspicuous) enough that every Christian can arrive at the correct interpretation. The fact that there are 30 000 denominations, each interpreting the Bible differently, is explained away by Protestants. They say this is because those who do not arrive at the correct interpretation of Scripture (the "correct" interpretation being the interpretation of whoever is making the accusation) are spiritually blind, by sin or some other reason.
The problem with this is obvious. Luther believed in baptismal regeneration, while Calvin did not. Who is blinded by sin? Calvin or Luther? According to Protestants, Luther was one of the greatest Christian thinkers who ever lived, and Calvin was a great Christian believer and hero. It must be hard for them to believe that either of them was spiritually blind (If they had their choice, Lutherans would say Calvin was spiritually blind, while evangelicals would say Luther was spiritually blind, but who is to decide?) It is more reasonable to say that the Bible is not clear enough regarding baptismal regeneration. We are all blinded by (original) sin, and therefore we need an infallible interpreter to unlock the true meaning of the Scriptures. If it is true that we are all blinded by sin, and therefore cannot interpret the Scriptures correctly, what good is that?
It was Luther's contention, when he first challenged the Catholic Church, that the Scriptures were so clear that every "milkmaid" and "child of nine" could understand it. When Calvin and other reformers came along and challenged his interpretations, he called the Bible a "heresy book". It was not long after their deaths that the book, 200 Interpretations of the Words, "This is my Body', was published in Germany.
Protestants respond by saying that the Bible is clear on the "essentials." They may differ on "secondary" beliefs, but since they agree on the essentials, the Bible is obviously clear in this area. First of all, the Bible does not label doctrines as being "primary" and "secondary". Secondly, it is not true that Protestants agree on the "essentials". Secondly, Luther believed in the Real Presence of Christ in the Eucharist, while Zwingli did not (Luther called him "damned" and "out of the Church" for this reason–it was obviously his belief that this was an essential doctrine). This was a primary doctrine, for Christ said, "Unless you eat the flesh of the Son of Man and drink his blood, you have no life in you" (John 6:53). Luther believed in baptismal regeneration, and therefore baptized infants, while Calvin did not, because he believed baptism was purely symbolic. This was an essential doctrine, as Jesus said, "Unless one is born of water and the spirit, he cannot enter the kingdom of heaven" (John 3:5). This is a salvation issue. Some Protestants believe in eternal security, while others believe one can lose his salvation. These are all primary doctrinal issues. And yet the Scriptures have not been clear enough for these Protestants; otherwise, there would be no disagreements. Either these issues are "non-essential", or the Scriptures are not clear enough. As Peter says: "Paul . . . wrote you . . . dealing with these matters as he does in all his letters. There are certain passages in them hard to understand, which ignorant and unstable people twist to their own destruction, as they do the rest of the Scriptures" (2 Pet. 3:15-16).