 A number of textbooks (Quine 1950b, some editions of Copi 1954, and Kalish &amp; Montague 1964, are perhaps the best known) employ a deviant set of quantifier rules. The simpler rules, \(\exists\)-I and \(\forall\)-E, are unchanged, but the two subproof-involving rules we just surveyed are replaced by rules which (following Quine) we will refer to as Existential Instantiation (EI) and Universal Generalization (UG):