Delineating the difficulties of predicting who will become a terrorist threat:

Any characteristic that is found among suicide bombers is likely to be found among many people who are not suicide bombers. The number of dissipated young men who turn arrogantly pious, for example, is likely to be a hundred times greater than that of suicide bombers. And this problem is likely to subsist, however refined the analysis becomes: the numerator will always be much smaller than the denominator. Moreover, surveillance itself will always remain fallible, however brilliant its successes. A friend of mine who works for the secret services assured me that there have been many more terrorist plots dismantled than the public knows about; but for most of us it is the plot that succeeds rather than the 10 or 20 that do not that counts. Only preventive detention for those with the identified characteristics of suicide bombers would eliminate the risk of any of them carrying out an outrage; but that would be to abrogate the rule of law.