Likewise, your decision, like anyone's, that the Bible is authentic (or whatever you want to call it) is yours.
Whether the decision is based on the witness of the Spirit within you, your own decision, or the decision of others, you still have to accept the decision of others, thus making it ultimately your own decision to trust THEM.
And how do you know THEY are correct? Did you decide all on your own that they are trustworthy? Or are you simply taking their say so on the matter of their trustworthiness?
How is trusting men any better?
You have no way of knowing with certainty that the true Spirit is within you.
Acts 8:17 "Simon saw that the Spirit was given through the laying on of the apostles' hands."
Has an apostle, or one of his successors, laid hands on you to receive the Holy Spirit? If not, you cannot assert with confidence what spirit it is acting in you.