Reflections on terrorism

We often face the questions: what is terrorism?, who should be considered a terrorist and who should be considered a militant? What forms does terrorism take?, does it evolve?, what threats does it cause?, can it be eliminated?, is it only a "private" domain, or is it also the domain of the state? What is its history?, how far back do its roots go, and will we ever get rid of it, and if so, how?