A Logical Reasoning rule of the form "If A, then B" (A → B), which is the backbone of grouping games and appears in many ordering and hybrid games. The non-optional protocol is to translate the rule into conditional form, immediately write the contrapositive (¬B → ¬A), and then check whether the rule chains with any other conditional. Because the contrapositive has equal logical force to the original, skipping it means accessing only half of the rule's information.