This book has involved scholars thinking historically about terrorism. In relation to the four main areas of understanding in the field – definition, causation, consequences and appropriate response - what can we therefore say that we know, and what should we prioritise next in our research? This chapter will identify some of what the contributors themselves have valuably argued, and it will consequently have a historical dimension. But it will also relate such ideas to wider understandings, findings and agendas, recognising that the study of terrorism is and should be collaborative between disciplines.