599. THE ISSUE OF PREVENTION – As established in the very beginning of this book, in the field of counter-terrorism, prevention is considered a must (see no. 3). Governments all over the world, the Belgian and UK governments included, have undertaken a myriad of initiatives in order to prevent terrorist attacks. Government intervention has indeed succeeded in apprehending certain people who had nefarious plans which, if left unchecked, would have caused civilian casualties and could have spread terror. However, prevention in itself is almost impossible to measure. It is extremely difficult to assess whether actions undertaken to avoid events taking place did actually succeed in their goal, as the fact that something did not happen does not mean the preventative action was successful. An infinite number of other factors may have played a role; establishing causality between a preventative government policy and the fact that terrorist attacks did not happen is therefore near impossible. This means that the exact impact and efficacy of a policy and especially of individual policy decisions is, and will most likely always remain, unknown. In this book we have assumed that restrictions to physical liberty can have a preventative effect, which seems to be a relatively safe assumption in general; but the inherent vagueness of prevention should always be kept in mind. Prevention is used by governments as the impetus to introduce many and far-reaching powers.