Shantila's Inside logic#1Imagine you are sitting in an airport, waiting for a late-arriving plane, when you hear a woman behind you say firmly yet quietly, "Ok. If you kiss me nicely, then I will marry you." "Really!" a man replies eagerly. Nobody says anything. You are curious what is going on. You turn around and peek -- and right away it dawns on you: She is going to marry him! * In that moment you have done something logical. You have reasoned. Your thinking developed in an orderly way. You heard a woman say some words (the promise), you saw something interesting (a kiss), and you put 2 and 2 together. We can say that you reasoned on the basis of hearing the promise and seeing the kiss. Your thinking here is logical. In reasoning our thoughts move from premises to conclusions. Your reasoning during those moments is based on these two premises.
And your conclusion is
You achieve something in this small act of reasoning. Your ability to do that is based on your understanding of how the little word "if" works in the sentence "If he kisses her nicely, she is going to marry him." Thought is so fast that we often are not aware of the transitions that take place. Logic focuses the spotlight on such transitions from premises to conclusions. Some transitions are good (as was yours in this example), others are bad, and others cannot be evaluated by logic. Usually we reason well in ordinary everyday situations. The bad transitions (when we do not reason well) could not occur if we did not reason correctly most of the time and in most situations. Your reasoning here is good because if your premises are true, the conclusions must be true as well -- which means your reasoning is valid. In other words, reasoning is valid when it is impossible for a conclusion to be false if all of the premises are true. Think about this example. Can you imagine any way the world could be so that both premises would be true, but the conclusion would not be true? Try to do it. That is, try to imagine it being true that if he kisses her nicely then she will marry him, and he does kiss her nicely -- but yet she isn't going to marry him. You cannot imagine this! It is impossible for the conclusion to be false if the two premises both are true. Your reasoning about the kiss is good, but this does not mean that the conclusion is true, since one or both of the premises may false (that is, not true). Logic alone does not establish the truth or falsity of conclusions and premises. As you sit there waiting for your plane, you might well wonder whether or not the couple ever really will get married. Are the premises true? Well, you are confident about the second premise, since you saw the kiss. You would need much more information about the situation to know whether or not the first premise is true. You do not know these people. Maybe she was lying in order to get a good kiss.. Or perhaps she was joking; perhaps this is a joke they often share, even though they both know that they are never going to get married. If you were curious enough, you could walk over and ask the couple about it and get more information. (But wouldn't that be a bit rude? After all, it is quite likely the promise and kiss were both sincere. Who wants you interrupting a moment like that?) Logic usually is not concerned with investigating the truth of premises. What logic is about, initially, is the fact that you can know, based on your reasoning, that if the two premises are true then indeed she is going to marry him. And you can know this even though you do not know whether both premises are true. This example of reasoning may seem like a small achievement. And, true, it is not much more impressive than adding 2 + 2 together to get 4. But it is not nothing. For consider how things would be for some guy, Joe, who couldn't reason at all using "if". Suppose he buys a lottery ticket and goes home to watch the lottery drawing on tv. The announcer twirls the balls and finally says, "If you have numbers 7 12 24 33 42 52, then you have just yourself won $8 million." When Joe hears that on tv, he thinks to himself,
He looks at his ticket, and thinks
Then he thinks, "Hm. I wonder if I won the $8 million?" Now remember that we are assuming (somewhat absurdly) that Joe cannot reason using "if" in the small way you did when you heard the woman and saw the kiss. So Joe does not reach any obvious and wonderful conclusion at all. He remains in the dark. He does not realize he has just won $8 million, even though all he needs to do is to think about it based on two premises he already believes. He may never realize that he won the lottery. That is how important logic is! The tv announcer is never going to say "Hey Joe --you just won the lottery!" The announcer doesn't know who won. In order to realize that he has won, Joe has to be able to figure it out for himself.
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