Oh, gotcha!

My one quibble, then, is that I don't think even subsidiary societies are entirely voluntary.  We can't choose where we are born, or to whom, or in what socioeconomic conditions, yet those have a dramatic influence on our development and our relationships within society.

Subsidiarity helps people choose what is best for them in matters of shared concern, but I don't think we can escape the fact that there *are* always matters of shared concern.  No man is an island.