Why disagreements when the Bible has clarity?

On page 111, Grudem asks "if the doctrine of the clarity of Scripture is true, why does there seem to be so much disagreement among Christians about the teaching of the Bible?"

On page 109 he seems to suggest two answers:

1. there are things on which the Bible is silent
2. we have misunderstood what the Bible is saying

While there are clearly areas where we can misunderstand, much of the weight of his argument in this chapter is that the Bible is basically understandable.

So I think the first option is an interesting one - I wonder how many things which we claim to be important in our church settings and Christian 'positions' are actually things built on church tradition (within a particular strand of church life) are things on which the Bible is silent or does not major.

If we claim that the Bible is the source of what we need in order to understand God's revelation of himself to us and in order to live as Christians (individually and collectively) then we need to guard against basing what we do / say on things which we believe to be there but actually aren't!