Over the past several years I have been working on a book, Migration And The Making Of Ireland. It examines how immigration, as well as emigration, has shaped life on this island since 1600 or so.
Much of the focus is on migrants who have arrived during the last few decades, such as Poles, Chinese and Muslims from many countries. There is also a focus on earlier groups, including Jews from what is now Lithuania, Huguenots and, of course, settlers from Scotland and England.
At an early stage in the writing I had a heated exchange with an irate friend on the proper use of terminology.
I used the term "migrant" to refer to settlers from Scotland, who were part of the early-17th century Plantation of Ulster. But he insisted that those who arrived in Ireland during the 17th century could not be described as "migrants".
Yet, the Plantation of Ulster included waves of settlement by ordinary labourers, artisans and by people whose descendants migrated onwards to North America as indentured servants.
Some of those who settled, or were planted, in Ireland had migrated in order to flee persecution elsewhere. Many of the Catholic Irish who emigrated from this island were no less part of settler overseas colonisation projects than those who came to Ulster from Scotland and England.
Emigration from Ireland mostly occurred to places that were, or had once been, part of the British Empire.
Both Catholic and Protestant emigrants became part of colonial systems as soldiers, policemen, administrators and as missionaries.
We should be careful, some historians advise, about concentrating too much on plantations in seeking to understand social change in 17th century Ireland.
We focus on plantations and their owners, because we have considerable documentary records of these and because we have far poorer records of how ordinary migrants who settled in Ulster lived their day-to-day lives.
For the most part, ordinary migrants remain invisible. We know, perhaps, where they came from and their range of occupations, but not their particular stories.
A pamphlet published in 1610 by Thomas Blennerhasset, an undertaker with 2,000 acres in Co Fermanagh, exhorted his fellow Englishmen to settle in Ulster, but only if they had the necessary skills and character.
Tradesmen, smiths, weavers, masons, carpenters and husbandsmen were needed and would succeed in Ulster.
Ministers of God's word were also needed. Poor, indigent fellows were advised to stay where they were; they would starve in Ulster.
Histories of the Ulster Plantations give considerable details of the landholdings, successes and failures of landowners and the lives of clergy, but when it came to ordinary settlers, these were thin on detail.
The stereotypes applied to subsequent generations of Ulster Presbyterians did not necessarily apply to their first generation settler ancestors.
Take for example the testimony of Andrew Stewart, who was the son of a Presbyterian minister who settled in the Six Mile Water Valley in south Antrim during the 1620s: "From Scotland came many, and from England not a few, yet all of them generally the scum of both nations, who for debt, or breaking and fleeing from justice, came hither, hoping to be without fear of man's justice in a land where there was nothing, or but little, as yet, of the fear of God."
Many of the Presbyterian ministers who went to Ulster prior to 1625 were disappointed to find many settlers fairly indifferent to religion. Presbyterianism did not flourish until a few decades after James's plantation.
In his 1914 book The Ulster Scot: His Religion, the Rev James Barkley Woodburn sought to explain this early ambivalence by likening early Scottish settlements to mining camps: "The first to emigrate to a mining camp are generally those who have not succeeded at home, or who have been in debt, or who are dissatisfied with their present condition."
Of course, such stereotypes may be no more true than ones associated with present day immigrants.
What many migrants share is a desire for a better life for themselves and their families, initiative and, perhaps, a sense of adventure.
In writing the book, the challenge has been to find similar ways of addressing the experiences of emigrants and immigrants across space and time, for all that different political, economic, cultural and religious contexts need to be understood.
The basic similarities between many migrant journeys make it possible to fruitfully examine both immigration and emigration in the same breath.
Most immigrants and emigrants who left, or came to, Ireland journeyed under circumstances that were not of their choosing.
They were often helped by family members, who had already come to, or left, Ireland.
Different religions have provided broadly similar support systems for emigrants from Ireland (Quakers, Presbyterians, Catholics and Jews) and among immigrants to Ireland (Jews, Pentecostals, Russian Orthodox and, more recently, Muslims).
The kinds of wider circumstances that push and pull migrants from one place to another recur again and again - be it the 17th century or the 21st century.
Bryan Fanning is Professor of Migration at University College Dublin. His new book, Migration And The Making of Ireland, is published by UCD Press, priced £20