Think back to an elementary school playground.  Often you could find a small group of girls sharing secrets with each other, giggling, whispering, etc...  When someone approaches that isn't part of the group, the girls scatter refusing to let the newcomer in on their secret circle.  

In Colossians 2 Paul is addressing a "secret knowledge" that brings division in the church.  Unity in the church is wrapped around love and the knowledge of Christ.  Walking in wisdom and discernment requires community.

Colossians 2:1-7