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Astralis said:

I think this may be the crux of the issue. What authority has the authority to teach? Mathison admits that Reformed traditions must appeal to tradition. But, how do you know what tradition to appeal to?

John Murray answers your question in the article Pilgrim suggested you might like to read.

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Murray writes:

Tradition is always subject to the scrutiny and test of Scripture. Its rightness or value is always determined by its conformity to Scripture. This is just saying that it is never proper to appeal to tradition as having intrinsically an authority in matters of faith or morals. Tradition when true and right and good always flows from the Scripture and is simply God's will as revealed in Scripture coming to expression in thought and life. Tradition, when right, is always derived; it is never original or primary. And this is invariably true from whatever aspect tradition is viewed.

There you have it! You've always got to go to the source, the Bible.

When I survey the wondrous cross on which the Prince of Glory died, my richest gain I count but loss and pour contempt on all my pride. - Isaac Watts