ABSTRACT
The unsuitability of textbook algorithms as psychological models stems in large part from one of their often-noted features, namely, the "material implication" sense of the conditional. Given the restriction that the model be relatively indifferent to formula interpretations, standard treatments of symbolic logic provide an obvious place to seek an account of the subjects' mental processes. The interest in symbolic logic derives in part precisely from its "contentless" rules of valid reasoning. Such a psychological model would be doubly valuable since the formal properties of many elementary logical systems are well-known. One may find encouragement for this line of investigation in the fact that a variety of algorithms exist for determining whether any formula of sentential logic or of Boolean term schemata, such as the experimental formulas, is tautological. An analogous anomaly for the logic of classes is the law that the empty class is a subset of all classes.
