“achieving strategic success requires relying on a logical argument, unless they want to depend on luck. By argument, we mean a chain of reasoning by which a conclusion is drawn from a set of assumptions or premises. By logical argument, we mean an argument that passes the test of logic. We define logic as reasoning conducted or assessed according to strict principles of validity.7 As we illustrate later, validity in this usage means that the premises automatically imply the conclusion: the chain of reasoning makes sense and is logical.”