The Rape of Jacob's Daughter Part 2/Canonicity

Following his completion of Genesis 34, Pastor Ty digresses into a discussion of canonicity, "How do we know we have the right 66 books in the Bible?

Something happens in Daniel 9 that has a lot to say about "canonicity"... the canon is the rule or the standard... that's what that Greek word meant, be a measuring rod. And the word "canon" has been used theologically in church history to mean the accepted rule concerning God's Word. What are the books that are the Word of God? That's the canon. And we believe there are 66 books in the Bible, and in fact in believing that we have great confidence that we have the 66 books that we should have...

Do we really have the New Testament books that were really the original New Testament books? How do we know what books are the canon? How do we really know?