Steven Pinker -- How the Mind Works - Hampshire High Italian ...

334 | HOW THE MIND WORKStrue, therefore P is true. P or Q is true, P is false, therefore Q is true. Pimplies Q, Q is false, therefore P is false. I can derive all these truths notknowing whether P means "There is a unicorn in the garden," "Iowagrows soybeans," or "My car has been eaten by rats."Does the brain do logic? College students' performance on logic problemsis not a pretty sight. There are some archeologists, biologists, andchess players in a room. None of the archeologists are biologists. All ofthe biologists are chess players. What, if anything, follows? A majority ofstudents conclude that none of the archeologists are chess players,which is not valid. None of them conclude that some of the chess playersare not archeologists, which is valid. In fact, a fifth claim that thepremises allow no valid inferences.Spock always did say that humans are illogical. But as the psychologistJohn Macnamara has argued, that idea itself is barely logical. Therules of logic were originally seen as a formalization of the laws ofthought. That went a bit overboard; logical truths are true regardless ofhow people think. But it is hard to imagine a species discovering logic ifits brain did not give it a feeling of certitude when it found a logicaltruth. There is something peculiarly compelling, even irresistible, aboutP, P implies Q, therefore Q. With enough time and patience, we discoverwhy our own logical errors are erroneous. We come to agree with oneanother on which truths are necessary. And we teach others not by forceof authority but socratically, by causing the pupils to recognize truths bytheir own standards.People surely do use some kind of logic. All languages have logicalterms like not, and, same, equivalent, and opposite. Children use and, not,or, and if appropriately before they turn three, not only in English but inhalf a dozen other languages that have been studied. Logical inferencesare ubiquitous in human thought, particularly when we understand language.Here is a simple example from the psychologist Martin Braine:John went in for lunch. The menu showed a soup-and-salad special, withfree beer or coffee. Also, with the steak you got a free glass of red wine.John chose the soup-and-salad special with coffee, along with somethingelse to drink.(a) Did John get a free beer? (Yes, No, Can't Tell)(b) Did John get a free glass of wine? (Yes, No, Can't Tell)Virtually everyone deduces that the answer to (a) is no. Our knowledgeof restaurant menus tells us that the or in free beer or coffee implies "not