From the early 1990s until the Belfast Agreement of April 1998, a new relationship between the actors at the centre of the Northern Ireland conflict was negotiated, formalized and agreed, to institutionalize the conditions of an historic accord. What happened is, in considerable part, a matter of interpretation and the selection of facts to support it. And how we interpret it depends on the theoretical premises and philosophical assumptions which we bring to bear on this – as on any – empirical event which we seek to explain and understand.

In roughly the same period of the 1990s, something happened in regard to American foreign policy and its impact on European security. The decade began with the bipolar relationship still in place, though immeasurably warmer and more cooperative than it had ever been during the Cold War. From early in 1994 until the NATO summit meeting in Madrid in 1997, the conditions were laid for an agreement between the sixteen member-states to expand the Alliance eastwards. Again, where we look for the facts and the reasons to explain this decision, and how we interpret its likely impact on security in Europe, depend on prior theoretical ideas about the unit actors and the nature of the constraints which influence them, about our capacity to explain human events in scientific terms; in short, about what kind of world we think we are living in.