Did the messengers who wrote scripture preach the gospel with clarity?
The "Iglesia Ni Cristo" teaches that one cannot understand the Bible without a messenger who is properly ordained to explain God's truth. From the INC's perspective, were the messengers that we read about in the Bible able to preach God's truth with clarity?
When we examine the INC's position as well as scripture itself, we see that the logical conclusion of the INC's position is that the Biblical messengers were not able to preach the gospel with clarity and that they were not sufficient messengers. To be clear, the INC would not say this directly, but in their teaching, they deny the ministerial authority of the biblical messengers.
According to the INC, the Old Testament messengers were sufficient messengers.
Let us take the example of David, who wrote many of the Psalms. The INC claims that David is a messenger of God. However, they also teach that we cannot understand the things he wrote. They make David to be a failed messenger.
According to the INC, the New Testament messengers were sufficient messengers.
If David's words were not good enough to explain himself, then that means we need another messenger to explain David. In Hebrews 3-4 we receive two chapters dedicated to explaining Psalm 95. The INC claims that the author of Hebrews is a messenger from God, but that his explanation of Psalm 95 cannot be understood without the help of a third messenger. The INC claims we need a messenger (INC minister) to explain a messenger (author of Hebrews) explaining a messenger (David)!
Culture doesn't fix the problem.
The INC might argue that the difference is that we are removed in time and place from the original writings of the Bible and so we need a messenger who speaks as we do, but this does not fix the problem. The Bible gives us no such reasoning. Additionally, the Bible has been translated into modern languages so that we can understand it. Cultural references do not utterly dominate the scriptures and when they appear, they typically provide their own explanation.
How could the INC possibly draw a line on cultural differences? A members culture is not the exact same as his ministers, and another may have an even more different culture, yet the INC does not say that this prevents a minister from preaching the gospel. At what point does a culture become so different that we need a new messenger to explain what the first one said? The INC has not bothered drawing any such line, and the reason is likely because they cannot.
Interaction doesn't fix the problem.
The INC might argue that we need a minister who can interact with us and answer questions, but this does not match what we see in the Bible. Many believed after hearing the message of the apostles without asking any questions.
Presence doesn't fix the problem.
The INC might argue that we need a minister who is present with us in order to explain the Bible. Not only is this a very arbitrary and non-biblical requirement, it also means that the apostles who communicated by writing were not able to successfully communicate with those who read their letters.
The INC's position on scripture taken to its logical conclusion denies the authority of the authors of scripture as well as the sufficiency of scripture. If they were truly messengers, they should be able to explain the word of God to us.
Instead of denying the authority and sufficiency of the word of God itself, let us read it, being like the Bereans.
Acts 17:10-11 (ESV) - 10 The brothers immediately sent Paul and Silas away by night to Berea, and when they arrived they went into the Jewish synagogue. 11 Now these Jews were more noble than those in Thessalonica; they received the word with all eagerness, examining the Scriptures daily to see if these things were so.