Introduction In this book, we have provided an overview of factors that play a role in polarization, radicalization and terrorism. Some of the literature we discussed is theoretical in nature and based upon past empirical research into intragroup and intergroup processes. Silke (2008) noted that only 1 per cent of publications in this field make use of systematic interviews with radicalized individuals. This has changed since then, but the percentage is still quite low. Only a few studies involve interviews, and they usually focus upon small samples of convicted terrorists (see e.g. Orsinsi 2013; Post, Sprinzak & Denny, 2003; Stern, 2004). Others, for instance Sageman (2004), draw upon public sources such as court records and media reports. Nonetheless, we can draw a number of conclusions from the extant literature. They are presented in this final chapter, after which we briefly discuss the importance of understanding the processes involved when developing possible interventions. In this chapter, we also attempt to assess where we stand regarding terrorism, where this field of research stands and where we need to go in future research. Finally, we touch on the relation between the struggle against terrorism and civil rights.