Diaspora is the non-voluntary scattering of a people from their homeland. The thesis surveys the current theory of diaspora by locating it within theory of migration, identifying characteristics of diaspora and a classification of diasporas. The thesis then extends present thinking on diaspora by developing conceptual consideration of the nature of oppression, Serial Diasporas, Virtual Diaspora, some quantitative aspects of diaspora and an Irish Literary Diaspora. A longing for the lost homeland is a prime characteristic of diaspora groups, and yet an actual return is very rare; the return of Jews from the diaspora is considered extensively to illustrate why such a return in significant numbers is unique. Throughout the thesis there is an engagement with problems of methodology and the validity of information and knowledge. Topics for further investigation such as strategies to ensure the survival of the diaspora and diaspora as a literary genre are presented. The thesis concludes by suggesting that a narrower definition of diaspora may be appropriate, and that diaspora is insufficiently recognised as a vital component of individual and group identity within contemporary societies.