C: A theoretical system stipulates design specifications of a sim­plified idealized system, with attributed powers and opera­ tions, intended to apply to empirical systems of a resemblance class, a restricted reference class. Deflections from the design specifications are considered departures from the ideal. Most research efforts involving a computational theory of mind have been devoted to capacities we are proud of-solving problems (Newell & Simon, 1972), planning (Sacerdoti, 1977), understanding stories (Dyer, 1983; Schank & Abelson, 1977). There are other mental capacities and liabilities we are not so proud of. Yet these departures are worth attention because they matter in human lives-misunderstandings, misconstruals, inhibited actions, misguided desires, and a variety of displacements and deflections from the ideal design. Extreme and enduring negatively valued deflections of mental systems represent conditions that may activate attempts at correction. Because they demonstrate striking values of the properties involved, resemblance classes of the extreme deflections are important for a cognitive science that needs taxonomically clear cases for computational explanation.