John Donne was having none of it -- or at any rate, as little as he could get away with. In an era when this absolute difference was actually enshrined in law, and yet more deeply in popular culture -- and when Anglicanism itself was torn sharply between its Puritan and Episcopalian sides -- he spent much of his ministry publicly walking a fine line.
On one hand, he was a Protestant's Protestant -- one of the Anglican representatives to the Synod of Dort, much travelled in Germany, disliked by Laud and given to taunting the Jesuits whenever he could. On the other hand, Donne had been raised Catholic in a family of martyrs (including not one but two Jesuits); his brother had died a prisoner for the old faith, his unconverted mother lived in the Deanery of St Paul's. Both Donne and his wife were relations of the celebrated martyr St Thomas More, and his movement to Anglicanism had been slow and painful.
It is not rare, in his preaching, for Donne to play with his auditors, coyly offering one side of himself, and depending upon them to remember the existence of the other. Our favorite example is this passage from a sermon on Acts 23:6-7, in which he expands upon Paul's exclamation to the Sanhedrin ("Men, brothers, I am a Pharisee!"). We have re-punctuated for clarity:
Beloved, there are some things in which all religions agree: the worship of God, the holinesse of life; and therefore, if when I study this holinesse of life, and fast and pray and submit my selfe to discreet and medicinall mortifications for the subduing of my body, any man will say “this is Papisticall, Papists doe this,” it is a blessed protestation, and no man is the lesse a Protestant nor the worse a Protestant for making it: “Men and brethren, I am a Papist; that is I will fast and pray as much as any Papist and enable my selfe for the service of my God as seriously, as sedulously, as laboriously, as any Papist.”
So if when I startle and am affected at a blasphemous oath as at a wound upon my Saviour, if when I avoyd the conversation of those men that prophane the Lord’s Day, any other will say to me “this is Puritanicall, all Puritans do this,” it is a blessed protestation and no man is the lesse a Protestant nor the worse a Protestant for making it: “Men and brethren, I am a Puritan; that is, I wil endeavour to be pure as my Father in heaven is pure, as far as any Puritan."
It is delightful to imagine the impact of such statements upon a congregation keenly sensitive to the language of theological partisanship. I am a Papist! I am a Puritan! They are shocked, thrilled, and at the same time relieved by their knowledge that he is neither.
It is the Anglican "middle way," of course (although Donne himself offered Lutheranism as a middle path between Papism and Calvinism), and a call to such unity in faith as may have been possible at the time. It is also the rhetorical device called coincidentia oppositorum, a cousin to the paradox by which some Lutherans call themselves "Evangelical Catholics."
But Donne's trope, in its cultural context, is far stronger than merely saying "I am A Protestant Catholic" or whatever. It is closer to a modern preacher saying "I am a Fundamentalist Liberal," but even that does not evoke the bare-knived enmity of the parties in question. Perhaps we could get the same effect by saying, if there were occasion to do so, "I am a Terrorist for Peace."