What is a Fool According to the Bible?

The Bible tells us that there are people who may be very intelligent, but in the end they are fools.  What makes them a fool, even though they are very intelligent and productive in several areas of their life?  And how should we deal with fools?  A few pages from the book of Proverbs will help us sort through this mess and give us a road map on how to deal with such people, and also how to avoid the things that make them foolish in God's sight.