It cannot be a subjective witness in the heart, because many would claim contradictory witnesses. There has to be an objective way of evaluating the matter. We need to have evidence that can demonstrate which belief is correct. I can assert my belief and you can assert your belief for eternity, but all we have in the end is two people arguing over beliefs that they offer no proof for. If courtrooms operated in the way that most theological discussions in the church do, every trial would be a waste because one lawyer asserts his belief in the innocence of the defendant, and the other in his guilt.
Evidence wins the case.
Evidence demonstrates the truth, not opinion. Most who believe in an inspired English translation tend to name the KJV as that translation. It is not the first major English translation. It cannot be by asserting our opinion. It cannot even be by looking at the sales numbers.