By Richard Jackson 
It has become something of a cliché to note that there are over 200 definitions of terrorism in existence within broader terrorism studies literature; that many terrorism scholars have given up on the definitional debate and use the term unreflectively; and that such a state of affairs hampers theoretical progress and skews terrorism research in unhelpful ways. However, the significance and consequences of the definitional debate go far beyond such narrow academic confines, important as they are to the field. Rather, the issue of definition is central to the way in which the Global War on Terror is prosecuted by the authorities both domestically and overseas. It also affects the way in which terrorism is understood and dealt with as a criminal act under international and domestic law. In the academic and cultural realms, the definition of terrorism has important implications for the way knowledge and commonsense about the subject is constructed and reproduced socially. Furthermore, it has substantial indirect consequences for individuals and groups labelled as terrorists – who may then be legally subject to torture, rendition and internment without trial – and for the ―suspect communities‖ they belong to.
This paper argues that despite a number of serious political and ontological obstacles to the definition of terrorism, it should be possible to agree on a clear set of criteria that can be employed to distinguish and conceptualise terrorism as a unique form of political violence. There are a great many advantages to adopting these definitional criteria. More importantly, there are political-normative imperatives for retaining ―terrorism‖ as a central organising concept for the field. The paper begins by discussing some of the main challenges in defining terrorism and the kinds of knowledge practices this has resulted in to date. The second section outlines a set of criteria that analysts can employ to distinguish terrorism from other forms of political violence. The final section of the paper attempts to demonstrate how this approach to terrorism can play a role in strengthening rules and norms against illegitimate and oppressive forms of political violence, whether it is committed by state or nonstate actors.
The Constitution of Terrorism
I have already noted that the definitional debate in terrorism studies has reached something of a stalemate. Not only is there no agreed definition among scholars, but an analysis of 490 articles published in the leading terrorism studies journals between 1990 and 1999 revealed that only eight, or 1.6 percent of them, could be regarded as conceptually-oriented papers.  This suggests that many scholars have largely given up on the challenging theoretical debates surrounding the central concept of the field. An examination of broader terrorism studies literature suggests four main approaches and practices towards the definition and conceptualisation of terrorism. Arguably the most frequent practice—particularly amongst scholars who are newly arrived to the subject—is to simply use the term without defining it, on the misguided assumption that it is widely understood and accepted. Such an approach is problematic for a number of very obvious reasons, not least because terrorism is a highly emotive and divisive concept which different scholars and societies have often understood in very different ways.
A second approach, confined mainly to political leaders and security officials, but also to a surprising number of researchers and media pundits, is to define terrorism as an ideology or movement. Although groups specializing solely in terror do sometimes form, they are
extremely rare and typically remain highly unstable and ephemeral. There are very few such groups operating today. In reality, most terrorism occurs in the context of wider political struggles in which the use of terror is one strategy among other more routine...