Benjamin Franklin's friend, the radical James Burgh, used the phrase "wall of separation" in his writings prior to Jefferson's, but isn't usually credited for it. If you have a chance, he's quite an interesting person to read. Quite strong on the subject of free speech. His 3 vol. POLITICAL DISQUISITIONS: OR, An ENQUIRY into public ERRORS, DEFECTS, and ABUSES. Illustrated by, and established upon FACTS and REMARKS extracted from a Variety of AUTHORS, ancient and modern. CALCULATED To draw the timely ATTENTION of GOVERNMENT and PEOPLE to a due Consideration of the Necessity, and the Means, of REFORMING those ERRORS, DEFECTS, and ABUSES; of RESTORING the CONSTITUTION, and SAVING the STATE. (London, 1774--75, available in an expensive reprint) is a masterpiece.
In Crito (1766, 1767. 2 Vols. Pp 92-3), Burgh proposed building "an impenetrable wall of separation between things sacred and civil":
"I will fairly tell you what will be the consequences of your setting up such a mixed-mungrel-spiritual-temporal-secular-ecclesiastical establishment. You will make the dispensers of religion despicable and odious to all men of sense, and will destroy the spirituality, in which consists the: whole value, of religion..."
"Shew yourselves superior to all these follies and knaveries. Put into the hands of the people the clerical emoluments; and let them give them to whom they will; choosing their public teachers, and maintaining them decently, but moderately, as becomes their spiritual character. We have in our times a proof from the conduct of some among us, in respect of the appointment of their public administrators of religion, that such a scheme will answer all the necessary purposes, and prevent infinite corruption;--ecclesiastical corruption; the most odious of all corruption."
"Build an impenetrable wall of separation between things sacred and civil. Do not send a graceless officer, reeking from the anus of his trull, to the performance of a holy rite of religion, as a test for his holding the command of a regiment. To profane, in such a manner, a religion, which you pretend to reverence, is an impiety sufficient to bring down upon your heads, the roof of the sacred building you thus defile."
Burgh is known for his explication of many issues, not only church-state separation and freedom of speech, but also gun ownership (2nd Amendment), standing armies (3rd) and rhetoric. Would love to see his Political Disquisitions, Crito, The Dignity of Human Nature (1754) and The Art of Speaking (1761) in print.
Just a thought.
cross-posted at Liberty & Power Blog