 The problem with Cook Wilson’s arguments is that they are based on an elementary confusion between membership of a class and inclusion of classes (see for example SI, cx &amp; 733–734). Peter Geach called Cook Wilson “an execrably bad logician” (Geach 1978, 123) for committing blunders such as this. (Cook Wilson’s claim in a letter to Lewis Carroll that it is not possible to know that ‘Some S is P’ without knowing which S it is which is P is another such elementary blunder (Carroll 1977, 376).)