Who is the Real Teacher?
Let's try this again. The other topic turned into a debate about what St. Augustine thought or did not think.
The more important issue of whether we can actually KNOW truth outside of revelation by God is the issue.
We can KNOW somethings because we have experienced them. For example, a child can be told by their parents that the stove is hot, and will burn them. The child, believing their parents may not touch the stove. At this point they do not KNOW the stove will actually burn them, but they trust their parents and believe what they say.
When they actually touch the stove (and most of us do) they suddenly KNOW that it will indeed burn them. They now KNOW this by experience.
The same can apply to KNOWING the truth of the Bible. Until we experience it as truth it is not something we actually KNOW.
This is what Jesus was referring to when He said unless we are born again from above we can not SEE the kingdom. Until the Holy Spirit enlivens our spirit, we may have read the Bible, attended church and with our minds believed what the preacher said. But until we receive the Holy Spirit and he brings the truth alive, we do not KNOW truth.
It is His witness that allows us to know truth from error when we hear someone teaching the things of God.
Scripture puts it this way:
1Jn 2:27 But the anointing which ye have received of him abideth in you, and ye need not that any man teach you: but as the same anointing teacheth you of all things, and is truth, and is no lie, and even as it hath taught you, ye shall abide in him.