Was St Patrick, in essence, a Protestant? Versions of that question have been asked for over four centuries and there are some who still ask it. A good place to start examining this long fascination is on 14 October 1932, during the closing stages of a conference organised by the Church of Ireland to commemorate the 1,500th anniversary of the arrival of Patrick. In a sermon preached at the final service, the Archbishop of Dublin, John Gregg, offered a strident defence of his church and its mission: The Church of Ireland is the most Irish thing there is in Ireland. It holds its apostolic ministry in unbroken descent from the Celtic bishops who succeeded Patrick. The Church of Ireland, then, was the true Irish Church, descendant of the father of Irish Christianity. Today [Gregg went on] the Church of Ireland turns neither to Windsor nor to Rome for the appointment of its bishops. It is an Irish self-governing organisation, as free from the intervention of Britain or the Vatican as the Celtic church was in the days of Columba.2 The Church of Ireland had regained its primitive independence, governing its own affairs for the spiritual benefit of the Irish people - a people, Gregg had to admit, the main body of [whom] refuse to be in communion with us. Nevertheless, the people should from time to time have plainly set before them the historical facts concerning the church which claims to be their own - those facts may set some of them thinking and asking pertinent questions.3 So, in 1932, the Archbishop of Dublin could assert that the Church of Ireland was the true heir of Patrick, that it enjoyed by right the independence and self-government of the early Irish Church and that if only people cared to acknowledge these historical facts they would see that true Catholicism was to be found not in Rome but with the most Irish thing there is in Ireland.4
McCafferty locates Ussher as chief spokesman in Ireland for the Protestant right to ecclesiastical tenure on that soil, answering the Controversialists question, Where was you Church before Henry Tudors lust imposed it on us? Is your Church not a foreign implant? (p.89)
Gives account of the Protestant scheme of history acc. to which the Church degenerated from its foundation, climactically with the loosing into the world of the Anti-Christ in 1000 AD, documented in Usshers Gravissimae Questionis de Christianarum Ecclesiarum (1613)
The religion of the papists is superstitious and idolatrous; their faith and doctrine, erroneous and heretical (The Protestation of the Archbishops and Bishops of Ireland against the Toleration of Popery Agreed Upon and Subscribed by Them at Dublin, the 26 of November 1626, London 1641.)
Calls Discourse not just intended as a scholarly rebuttal of Catholic claims [but] an evangelical torch to dispel the Antichristian darkness of Rome. 
The religion professed by the ancient bishops, priests, monks, and other Christians in this land waws for substance the very same with that which [now] by public authority is maintained therein [Whole Works, VI, p.238; here 90]
The Discourse was intended to rescue Catholics not to fuel fraticidal strife between Protestants. 
Because he tended to use evidence from Britain as ancillary to that from Ireland, Ussher could show that while there was cordial agreement between the Irish and British Churches, the tradition of the Church of Ireland still descended directly from Patrick. Thus his own Church of Ireland was autonomous, under its Primate, answering only to Charles I - but Charles as King of Ireland, not King of England. Elsewhere in the Discourse, Ussher was at great pains to prove that the kingdom of Ireland was no sixteenth-century fabrication of Henry VIII, but a thing attested from the much earlier times. (Discourse) The book intended to demonstrate that it was an act of profound patriotism to be a member of the Church of Ireland. Acknowledgement of the Popes power in matters spiritual was nothing less than an affront to the ancient dignity of the kingdom of Ireland. The whole of the Discourse is peppered with expressions such as our ancestors, our Patrick, our Brendan, our ancient church - all calculated to inspire pride in the country and in its national church. (Discourse) 
Prayers for the dead dismissed as prayers for those not doubted to be in heaven 
McCafferty delineates the ways in which ussher approximates his conception of early Irish ecclesiastical organisation and religious doctrine to the condition of the seventeenth-century Crhuch of Ireland, dealing with the question of celibacy, transubstantiation, and monastic organisation, which he conceived of as a sort of seminary so that the monasteries seemed like so many proto-TCDs and the monks in them so many dons 
Patrick had special regard for Rome which was entirely justified in those days before corruption, he acknowleged no dependence on the See, nor did he believe that Rome had any special privilege attached to it; see John McCafferty, St Patrick for the Church of Ireland: James Usshers Discourse, in Irish Studies Review, April 1998, p.95].
Ussher: They did not only consecreate bishops but also erected new bishoprics and archbishoprics too sometimes (Works, IV, p.322-23).
The stumbling block presented by the twelfth century was considerable. On the one hand, it was a time when the church in Ireland could, through a series of synods, be said to have acknowledged the suzerainty of Rome and to have caused the dominion of Antichrist to spread across the land. On the other hand, Ussher knew that the current diocesan system had been erected by these same synods. Around the same time came conquest and the rule of Henry II, but along with these political events went the licence of the papal bull lwaudabiliter. Ussher had the tough task of having to smash Laudabiliter, condemn the popes presumption in making such a grant, but not diminish in any way Henry IIs title to Ireland. He was forced to play up the submission of the Irish episcopacy to Henry as king and lord in 1171. The conjunction of assumption of power by the Roman Antichrist over Ireland with the arrival of the English king was a messy and unfortunate business, and with his providential scheme of church history, Ussher sought to divert attention from the potentially destructive clash of his political loyalties. He was wide open to the taunt that Antichrist and English rule came very close to one another, as well as to the more mundane charge that the title of the English king had been dependent on the papacy. The diversion came in the form of a blistering attack on OSullivan Beare (with whom Ussher had already crossed swords) and a trenchant (though uncharacteristically unsubstantiated) assertion that twelfth-century Ireland was esteemed a kingdom, and the kings of England accounted no less kings thereof. (Works, IV, 369) 
Ussher had a final word for the reader, a warning against a trite reading of his work: ’[T]he adversary must not imagine that I intend here to make such simple collections as these - that such a man held such a point with us: therefore he was a Protestant or such a man was a monk, or in such or such a particular agreed with the now church of Rome: therefore he was a Papist’. (Works, IV, 375). With this final reminder, then, that the weight of the evidence is what counts, Ussher gives us an elegant ending which rejects the crudity of polemic. He pleads: ’my intention... being to deal fairly and not desire the concealing of anything... that may tend to the true discovery of the state of former times... [even] if it may seem to make against me’.38 The agenda here is complicated. By retreating back into the pose he adopted at the start, and assuming the voice of a detached investigator, turning up evidence for the readers to judge for themselves, Ussher was drawing on a distinction between the historian and the antiquarian. By providing a list of his sources and explaining the way he had arranged his evidence, he wished to show that he was concerned with truth rather than controversy. There is no dishonesty whatsoever here. Ussher truly believed that the Church of Ireland was the heir of Patrick, and his attempt to portray it in that light was, as far as he was concerned, no more than sincere description of the past. 
Holds that Usshers model of church history, based on the Protestant traditions of his period, was already outdated since the coming versions of the reformation tended to be legalistic rather than apocalytic. 
Ussher gave the Church of ireland an origin legend, an impeccable ecclesiastical pedigree, and he did it by depicting Patricks Church as one that endured even through threat and persecution. 
Ftn. quotes Usshers argument that Ireland was counted as one of the four antique kingdoms of Europe at the Council of Constance, adding, ;And this I have ghere inserted all the more willingly, because it makes something for the honour of my country, to which, I confess, I am very much devoted. (Whole Works, IV, 369-70.)
Bibl. incl. Ute Lotz Heumann, The Protestant Interpreation of History in Ireland: The Case of James Ussher, in B. Gordon, ed., Protestant History and Identity in Sixteenth Century Europe, Vol. II: The Later Reformation (Aldershot 1996), pp.107-20; Alan Ford, The Protestant Reformation in Ireland, 1590-1641 (Franfurt 1987); Declan Gaffney, The Practice of Religious Controversy in Dublin 1600-1641, in W. J. Shiels and Diana Ward, eds., The Churches, Ireland and the Irish (London 1989), pp.145-58; Bernadette Cunningham, The Culture and Ideology of the Irish Franciscans at Louvain 1607-1650, in Ciaran Brady, ed., Ideology and the Historians (Dublin 1991), pp.11-30; C. R. Elrington and J. H. Todd, eds., The Whole Works of James Ussher, 17 vols. (Dublin 1847-64); Alan Ford, The Church of Ireland 1588-1641: A Puritan Church?, in A. Ford, J. I. McGuire, and K. Milne, eds., As by law Established (Dublin 1995) [q.pp.]; for discussion of Dempster controversy, see Joep Leerssen, Mere Irish and Fíor Ghael, 2nd ed. (Cork 1996), pp.263-77; Bernadette Cunningham and Raymond Gillespie, The most adaptable of saints: The Cult of St. Patrick in the Seventeenth Century, in Archivium Hibernicum, Vol. 49 (1995), pp.92-93; McCaffrey, God bless your free Church of Ireland: Wentworth, Laud, Bramhall and the Irish Convocation of 1634, in J. F. Merritt, ed., The Political World of Thomas Wentworth, Earl of Strafford (Cambridge 1996), pp.187-208; Joep Leerssen, Archbishop Ussher and the Gaelic Past, in Studia Hibernica, Vols. 22-23 (1982-23), pp.50-58; William Monck Mason, The Catholic Religion of St. Patrick and St. Columbkill (Dublin 1822); Nelson McCausland, Patrick Apostle of Ulster: A Protestant View of St. Patrick (Belfast 1997).