What is the difference between a church and a social club? There is a popular line that exists in sermons (heck, I've even preached it myself!) that says something to the effect of "a church is not a social club."  A church is not the local Kiwanis, it is not the local Boy Scouts, and it sure as heck isn't supposed to just be another "community center."

But how?

In what concrete ways is a church different than any other faternal or social organization?
The Church is presented as the Body of Christ (an organism, not an organization [e.g., 1 Cor. 12:12+]) and as the household of faith (a family, not a club [e.g., Gal. 6:10]--also sons of God, brothers and sisters).  As the Body of Christ there is an implication of a different kind of life (this may address a spiritual nature), an implication of diversity (different parts), unity (one body), and completeness.  Both the body and family metaphors point to the lack of choice of individual members in who else is part of the collective--one does not choose one's relatives.  Both also point to a fundamental identity in and with the whole (an eye cannot just pop itself out and reject its being part of the body; the parts suffer together and rejoice together).

On a practical level, this should mean that the common boundaries of social status, personal interests, etc. should not be separating factors in the Church as they tend to be in social organizations (e.g., Gal. 3:28).

The fact that the Church is God's (new) creation rather than a human formation (e.g., John 1:12-13) also has implications for persistence(e.g., Phil. 1:6), righteous action (e.g., Eph. 2:10), and ultimate success (e.g., 1 John 3:2).  (This might be analogous to the difference between Scripture and human writings.)  (The Church might also be viewed as something like the Holy Spirit as "earnest" or the resurrection of Christ as a first fruits--a sample of what the new creation in its fullness will be like and an assurance that this fullness is coming.)