Hacker initially emphasized two dimensions for classifying individual categories of terrorists. These dimensions are selfishness/unselfishness and self-protective/non-protective. According to Hacker, the crusader is non-protective and unselfish; the criminal is self-protective and selfish; and the crazie is non-protective and selfish. However, Hacker fails to discuss the fourth possible classification: the person who is unselfish, but self-protective. Such a classification would be useful less as a psychological type than as a sociological role classification. Thus, potential careers for the calculator might include the revolutionary, the government-sponsored nationalist, the private-sector nationalist, the religionist, the racist, the anarchist, the searcher, the romantic, the munitions dealer, and the representative of an international crime group. In a 1979 paper, Hacker suggested the possible existence of a calculator, through his comment that a crusader is blindly obedient to someone. Thus, adding this category would be a useful way of demonstrating a role separate from that of crusader. Appended chart and 10 reference notes.