Oh...but we do.  Reason tells us so much.  

You're taking a rather fundamentalist / rigorist approach to knowledge of Jesus.

But God gave us much more than the few words of Jesus we have.  He also gave us much more than all of Scripture, which also reveals His nature, and His will for us.

He gave us our reason!

This is what Catholic fundamentalists such as your comment represents miss.

- We know that Jesus was perfect man and perfect God.  He possessed all the human virtues in their most complete and perfected state.
- We know that Mary and Joseph prayed a lot..every dinner conversation with Jesus was of the most intimate form of prayer imaginable.
- We know how "attractive" Jesus was...his human and divine nature drew people to Him, so curious and in awe were they..lots of Scriptural examples.
- We know that Mary was full of grace, and Joseph as a just man, and had a bit of reputation as a craftsman.
- Reason tells us much, that your fundamentalism misses.