To expand on this. At first glance, we don't know what value Anne has. But marital status is a boolean value. Since marital status is boolean, it follows by th

To expand on this. At first glance, we don't know what value Anne has. But marital status is a boolean value. Since marital status is boolean, it follows by the Law of the Excluded Middle that Anne is either {married | unmarried}. If we brute force the question by simulating each possible value that Anne can assume (and follow the implications), we arrive at the correct answer. But imagine a case where we test for flavors of ice cream rather than marital status. > Jack is looking at Anne, but Anne is looking at George. Jack has chocolate ice cream, but George has vanilla ice cream. Is a person with chocolate ice cream looking at an person with vanilla ice cream? Can we correctly answer the new question? No, because Anne might have strawberry ice cream. A flavor isn't a boolean value! Also consider that simulation (especially when exhausting every possibility) expends a lot of energy. Therefore, the default strategy is to use a heuristic. And the heuristic is chosen by pattern-matching the "feel" of the question. Unfortunately, the feel of the original question doesn't trigger a heuristic which takes into account the boolean nature of marital status. So rather than assign Anne a value of {married | unmarried}, we assign Anne a value of {null} and call it a day.