As a man of the fifth century, Patrick would be appalled and mystified by us all. He might recognise that some of us still wear wool but almost nothing else of us on this island would be familiar to him; not our speech nor our eating habits, let alone our technology.
But were he to sit down with some devoutly religious people and discuss theology he might find some kind of affinity with some of them.
In his day, Mohammed had not yet been born so he might be curious about the tensions between Christianity and Islam.
He would be equally perplexed by some of the Christians claiming that God had been sending Mary, the Mother of Jesus, down to us with messages about the need to revere priests and keep the peace.
It might puzzle him that these visitations had only been happening in the last hundred years or so.
Catholics would be confronted with the paradox that Saint Patrick was oblivious to much that they hold dear. Fatima, Lourdes, Knock and Medjugorje would mean nothing to him.
The doctrine of the Immaculate Conception, by which it is understood that Mary, alone among all humans, was born without original sin, would be something that he would have to discuss a little further before he could decide that he was still theologically tied into the Church of Rome.
And what would he make of the more recent doctrine that Mary never died but that she was assumed bodily into Heaven, from where she returns from time to time?
It is hard to escape the conclusion that so much of what Catholics believe now would be as strange as Islam to Patrick.
It has been argued before that Patrick would probably feel most at home among members of the Church of Ireland.
Well, he would expect Christians here to respect an episcopalian structure, so maybe that is where he would be most at home. But he would not have lived through the Reformation and would wonder how Anglican bishops derived their authority from the Apostles.
How would he respond to the reverence shown by Anglicans to the British monarchy? What would he make of churches that commemorate battles and drape British national flags?
If he was to ask Protestants what it was that they had protested against, would he agree with them?
He might have similar difficulty adjusting to the religious culture of the evangelicals and Pentecostalists, but he should at least understand what they were talking about when they were not speaking in tongues.
They would tell him that they were closer to the spirit of the Gospels than the others and he might agree with them on that, but he had belonged to a church with a hierarchy. What would he make of lay pastors mediating the Bible to small groups in parish huts or to mass rallies in grandiose halls? I think he would wonder who the top man was.
He was a bishop himself in his time and he might expect to be deferred to.
Then there is the question of whether Patrick would be a nationalist or a unionist? Travel in his day was easier by sea than land so he would have felt closer to the coastal communities of Britain and Scotland and to the islanders than to the Irish of the midlands. So he probably would not have understood the need to define a nation by its physical territory.
Would he even have known what shape the island of Ireland was?
He never knew any coherent authority over the island. He might take time to grasp the complexity of our current tribal rivalries, but the news that we were still divided would come as no surprise to him.
Ours is not Patrick's world. It would be entirely alien to him. Irish people of different traditions will be claiming him today as their patron, their inspiration and their guide.
They may all be grateful though that he is not around to contradict them but that he is far in the past, where he belongs.