Then who wrote down the oral? Did every word the apostles or Christ say was written down somewhere that you have at your disposal? Many of the things have been headed down by the early Church fathers. Have you read any of them to see what the early Christians actually believed? If you do not know what they believe who were taught the oral teachings then how do you really know what the Apostle mean by what is written down or are you trying to say what is in the bible is all the Apostles ever said for those 70 years after Christ rose.
Open your Bible and look at who the Holy Spirit used to write what is known as Scripture and the book we call the Bible. Hope that helps. The Scriptures are the revelation that God has given to man about the way of salvation and godly living. If revelation is continuous and ongoing, then who has this extra revelation? The JW’s, the Mormons, or all of them? Wether 50, 100, 500, or 1700 years afterward does not make any difference if the claim is extra revelation. Not everything the Apostles ever said is inspired, if it were so we would have it in the Scriptures; we have exactly what God wanted us to have and the topics of sin, repentance, salvation, sanctification, godly living are all consistent and is what God wanted us to know.
The Holy Spirit is not just the author of Scripture but the illuminator of Scripture - 1 John 2 verse 20 But you have an anointing ***{the Holy Spirit} ***from the Holy One, and you know all things. verse 21 I have not written to you because you do not know the truth, but because you know it, and that no lie is of the truth…verse 27 But the anointing
{Holy Spirit} which you have received from Him abides in you, and
you do not need that anyone teach you; but as the same anointing {Holy Spirit} teaches you concerning all things, and is true, and is not a lie, and just as it has taught you, you will abide in Him.
John 14 & John 15 and turn to 1 Corinthians 2 beginning in verse 9 But as it is written: “Eye has not seen, nor ear heard, Nor have entered into the heart of man The things which God has prepared for those who love Him.” 10 But God has revealed them to us through His Spirit."
This was borrowed from Isaiah, but these things are unavailable to the unregenerate, but to Christians, it is known. Reading further the spirit who is from God is given by the Spirit…and verse 12 sums it up “Now
we have received, not the spirit of the world, but the Spirit who is from God, that we might know the things that have been freely given to us by God.”
As far as the early church fathers, were they infallible? How can you know what parts they said were true and the parts that were not if one has no superior standard by which to compare, which is the Scriptures? How do you know you are not misunderstanding what they said without directly having the ability to ask them what they meant by what they said since what they spoke are not inspired unless you have a standard to compare it to? This is why the Scriptures are superior to all.
How as Christians can one tell if the preacher is teaching error if not for the power of the Holy Spirit giving the Christian the ability to tell the difference between truth and error. The problem in the church today is that no one cares about reading and studying the Bible and acting like those Bereans to see if what is taught is true or not. Either way; if one is not a Christian; no amount of reading or studying will render one into the truth because the non-Christian is a natural man that cannot understand the things of God, but the Christian, who has the mind of Christ is able to tell or understand truth from error according the Holy Spirit and is judged by no one because the judge of all has already removed the Christians deserved damnation judgment onto Christ on behalf of the Christian. — see 1Corinthians 2