One sometimes finds Protestants, especially those in the Republic of Ireland (where I live) and Northern Ireland, attempt to present St. Patrick (385-461) as a proto-Protestant. The problem is that, apart from being a calumny against him, is also, as with many Protestant appeals to history, utterly bogus. Patrick believed in baptismal regeneration, invocation of saints and angels, rejected eternal security, and the salvific necessity of partaking of the Eucharist. While not problematic for some Protestants, his not being a cessationist would also be problematic, especially for the Reformed camp as would his acceptance of consecrated virgins.
Note the following, taken from The Writings of Patrick the Apostle of Ireland (Christian Classics Series VI; trans. Charles H. H. Wright; London: Religious Tract Society, 1894)
Patrick did not believe in Eternal Security
Although I am in many respects imperfect, I wish my brethren and acquaintances to know my disposition, and that they may be able to comprehend the wish of my soul. I am not ignorant of the testimony of my Lord, who witnesses in the Psalm, ‘Thou shalt destroy those that speak a lie.’ And again, ‘The mouth that belieth killeth the soul.’ And the same Lord says in the Gospel, ‘The idle word that men shall speak, they shall render an account for it in the day of judgment.’ Therefore, I ought earnestly with fear and trembling to dread this sentence in that day when no one shall be able to withdraw himself, or to hide but when we all together shall render account of even the smallest of our sins before the tribunal of the Lord Christ. (Confessions, I.3 [p. 38])
And I believe I was aided by Christ my Lord, and His Spirit was then crying out for me, and I hope likewise that it will be thus in the days of my oppression. (Confessions, II.9 [pp. 44-45])
If the Lord will, and if He will keep me from every evil way, that I may not sin before Him. But I hope (to do) that which I ought; but I trust not myself, so long as I am in ‘this body of death;’ for strong is he who daily tries to subvert me from the faith, and from the chastity of religion proposed (to myself), not feignedly (which I will observe), even to the end of my life, to Christ my Lord. But the flesh, which is in enmity, always leads to death, that is, to unlawful desires to be unlawfully gratified. And I know in part that I have not led a perfect life, as other believers. But I confess to my Lord, and I do not blush before Him, because I lie not: from the time that I knew him in my youth, the love of God and His fear have increased in me; and until now, by the favour of the Lord, ‘I have kept the faith.’ (Confessions, IV.19 [pp. 57-58])
In this hour of hours,
I place all those powers,
Between myself and every foe,
Who threatens my body and soul
With danger or dole;
To protect me against the evils that flow
From lying soothsayers’ incantations;
From the gloomy laws of the Gentile nations;
From heresy’s hateful innovations;
By these my defenders,
My guards against every ban--
And spells of smiths, and Druids, and women;
In fine, against every knowledge that renders
The light Heaven sends us, dim in
The Spirit and soul of man! (St. Patrick’s Hymn Before Tara, VI [pp. 97-98])
I place all those powers,
Between myself and every foe,
Who threatens my body and soul
With danger or dole;
To protect me against the evils that flow
From lying soothsayers’ incantations;
From the gloomy laws of the Gentile nations;
From heresy’s hateful innovations;
By these my defenders,
My guards against every ban--
And spells of smiths, and Druids, and women;
In fine, against every knowledge that renders
The light Heaven sends us, dim in
The Spirit and soul of man! (St. Patrick’s Hymn Before Tara, VI [pp. 97-98])
May Christ, I pray,
Protect me today,
Against poison and fire;
Against drowning and wounding;
That so in His grace abounding,
I may earn the preacher’s hire! (St. Patrick’s Hymn Before Tara, VII [p. 98])
Protect me today,
Against poison and fire;
Against drowning and wounding;
That so in His grace abounding,
I may earn the preacher’s hire! (St. Patrick’s Hymn Before Tara, VII [p. 98])
Grant us, O Lord, Thy grace and salvation! (St. Patrick’s Hymn Before Tara, XI [p. 99])
The Salvific Efficacy of Baptism and the Eucharist
Perhaps they do not believe that we have partaken of one baptism . . . Thanks be to God, baptized believers, ye have passed from this world to Paradise! (Epistle to Coroticus, 9)
And Patrick said: ‘Do you believe that the sin of your father and mother is taken away by baptism?
They replied: ‘We do believe it.’
[Patrick] ‘Do you believe that there is repentance after sin?’
[Daughters] ‘We do believe it.’
. . .
And they begged to see the fact of Christ. And the saint said to them: ‘Unless you shall have tasted death, you cannot see the face of Christ, and unless you shall receive the sacrifice’ (instead of ‘the sacrifice,’ the Tripartite Lie has, ‘unless you receive Christ’s body and His blood.’) (The Story of Patrick and the Royal Daughters [pp. 87-88])
Patrick did not believe, at justification, one’s then-future sins were forgiven
But hence I ought to give thanks without ceasing to God, who often pardoned my ignorance (and) my negligence, even out of place, not in one instance only—so that He was not fiercely angry with me, as being one who was permitted to be His helper. (Confessions, V.20 [pp. 59-60])
Invocation of Angels
I bind myself today,
To the power of the ranks of cherubim. (Stanza 3 of “The Hymn, or ‘Breastplate’ [p. 32])
May the host of God attend me,
And ward me,
And Guard me,
Against the wiles of demons and devils;
Against temptations of vice and evils. (St. Patrick’s Hymn Before Tara, V [p. 97])
Clericalism
I did not know the true God; and I was taken to Ireland in captivity with so many thousand men, in accordance with our deserts, because we departed from God, and we kept not His precepts, and were not obedient to our priests, who admonished us for our salvation. (Confession, I.1 [p. 36])
Therefore it is very necessary to spread our nets, so that a copious multitude and crowd may be taken for God, and that everywhere they may be clergy, who shall baptize and exhort a people needy and anxious. (Confessions, IV.17 [p. 55])
Consecrated Virgins
Whence, then, has it come to pass that in Ireland they who never had any knowledge, and until now have only worshipped idols and unclean things, have lately become a people of the Lord, and are called the sons of God? Sons of the Scots and daughters of chieftains are seen to be monks and virgins of Christ. (Confessions, IV.18 [p. 56])
For though I am unskillful in names, yet I have endeavoured in some respects to serve even my Christian brethren, and the virgins of Christ, and religious women . . . (Confessions, V.21 [p. 61])
Patrick was not a cessationist
And there indeed one night, in my sleep, I heard a voice saying to me, ‘Thou fastest well [fasting so], thou shalt soon go to thy country.’ And again, after a very short time, I heard a response saying to me, ‘Behold, thy ship is ready.’ And it was not near, but perhaps two hundred miles away, and I never had been there, or was I acquainted with any of the men there. (Confessions II.6 [p. 42])
But hence I ought to give thanks without ceasing to God, who often pardoned my ignorance (and) my negligence, even out of place, not in one instance only—so that He was not fiercely angry with me, as being one who was permitted to be His helper. And yet I did not immediately yield to what was pointed out to me, and (to) what the Spirit suggested. (Confessions, V.20 [pp. 59-60])
Patrick was most definitely not a Protestant or "proto-Protestant"; granted, he was not a proto-Latter-day Saint, nor would I dare suggest such, but it is intellectual dishonesty for those Protestants who suggest Patrick was "Protestant" in his theology.