Religion in the Republic of Ireland
Christianity is the largest religion in the Republic of Ireland based on baptisms. Irish Christianity is dominated by the Catholic Church, and Christianity as a whole accounts for 82.3% of the Irish population. Most churches are organized on an all-Ireland basis which includes both Northern Ireland and the Republic of Ireland.
Irish travellers have traditionally adopted a very particular attitude to the Catholic Church, with a focus on figures such as "healing priests". More generally a tradition of visions continues, often outside of Church sanction.
Catholic Church in Ireland
The Roman Empire never reached Ireland; so when the Edict of Milan in 313 AD allowed tolerance for the Levantine-originated religion of Christianity and then the Edict of Thessalonica in 380 AD enforced it as the state religion of the Empire; covering much of Europe (including Roman Britain); the indigenous Indo-European pagan traditions of the Gaels in Ireland remained normative. Aside from this independence, Gaelic Ireland was a highly decentralised tribal society, so mass conversion to a new system would prove a drawn out process.