James Madison on church-state separation

"It may not be easy, in every possible case, to trace the line of separation between the rights of religion and the Civil authority with such distinctness as to avoid collisions and doubts on unessential points. The tendency to usurpation on one side or the other, or to a corrupting coalition or alliance between them, will be best guarded agst. by an entire abstinence of the Govt. from interference in any way whatsoever, beyond the necessity of preserving public order, and protecting each sect agst. trespasses on its legal rights by others."

-- Letter to the Reverend Jasper Adams, January 1, 1832.