This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book explores the implications for the development of Irish Catholic identity as preserved in Irish language texts from the early modern period until the end of Stuart pretensions. It examines the issue of cultural Catholicism in the later middle ages, by way of devotional cults and practices. The book demonstrates that certain sections of the Catholic clergy and laity were prepared to welcome and implement the militant and warlike aspects of the Catholic Counter-Reformation. It points to the fact that some of the settlers were Catholic, most significantly the earl of Abercorn from Scotland and the earl of Castlehaven from England. The book examines Catholic unionism vis-a-vis Victorian politics, military and imperial service, the crown, and the position of the Catholic Church with relation to the structures of the state in Ireland.