Sandra Dodd

Rules are about what to do and when and where.
Principles are about why things are done and how.

http://sandradodd.com/rules
http://sandradodd.com/principles

That questions has been discussed at length by many different
writers, and those two links lead to quite a bit of writing on that
topic. That was freely available and could have been easily found by
anyone who searched on google for unschooling and principles.

Sandra