In order to think effectively, it is necessary to think in a logical manner. Logical thinking is thinking that employs valid reasoning to reach a correct conclusion.
Logical thinking is the foundation ofrational thought,thought that fits the real world and allows us to function well in it. There are two basic kinds of reasoning involved in logical thinking: inductive reasoning and deductive reasoning.
Inductive reasoningis characterized by making observations and gathering information until a general conclusion is reached. It is the basic method of sci- ence. About 500 years ago the astronomer Nicholas Copernicus made observa-
tions that led him to formulate the heliocentric theory of the solar system. About 150 years ago the botanist Gregor Mendel raised sweet peas, studied the charac- teristics of their flowers, and formulated his theory of heredity.
When a detective gathers clues and reaches the conclusion that the butler murdered the millionaire, the sleuth is using inductive logic. (When Dr. Watson asks Sherlock Holmes how he reached a conclusion, Holmes answers, “Deduc- tion, my dear Watson. Merely deduction.” Strictly speaking, he was using induc- tion, not deduction.)
Inductive reasoning also appears frequently in everyday life. Harold makes a series of observations about his car. It’s using too much gas, it’s pulling to the left, it’s overheating, it’s squeaking too much, and the brakes are mushy. He concludes that it’s overdue for servicing. Or perhaps he concludes that he needs a new car.
Rowena makes a series of observations about her fifteen-year-old daughter, Geor- gia. Her grades are falling, she is spending more time than usual talking secretively on the phone with one of her friends, she is dressing very carefully for school, she is reading romance novels, and she seems unusually dreamy-eyed. Perhaps Rowena, using inductive reasoning, reaches the conclusion that Georgia is devel- oping an interest in adolescent males.
(a) Logical thinking is thinking that employs to reach a correct conclusion.
(b) What kind of reasoning is characterized by making observations and gathering informa- tion until a general conclusion is reached?
Answers: (a) valid reasoning; (b) Inductive reasoning.
Deductive reasoning is reasoning in which a conclusion follows from a premise. The underlying structure of deductive reasoning is if-then.Such reasoning allows for predictions, and it is often the next step taken after inductive reasoning is employed. Sherlock Holmes tells Dr. Watson, “If the butler is really the mur- derer, then if we hide in the closet we should see him sneak into Jillian’s bedroom when the clock strikes midnight.” Rowena thinks, “If Georgia is getting interested in boys, then it won’t be long before she will be asking me if she can go on a date.”
According to Freud, there is a kind of thinking employed at the unconscious level of the mind that is overly primitive. It is neither inductive nor deductive.
Freud called this kind of thinking predicate thinking.It is also called paleolog- ical thought,meaning “old” thought. It is presumably the kind of thinking used by primitive, prescientific people and by preschool children. According to Freud, when two sentences have identical predicates (i.e., “first parts”) the objects or peo- ple in the sentences become associated in an illogical manner. Here is an example:
1. Automobile make X is driven by beautiful people.
2. Automobile make X is the kind of car I drive.
3. Therefore I am a beautiful person.
(a) What kind of reasoning is characterized by a conclusion that follows from a premise?
(b) According to Freud, what kind of thinking is neither inductive nor deductive?
Answers: (a) Deductive reasoning; (b) Predicate thinking (or paleological thought).
Predicate thinking is not the only way in which thinking can be led astray. Logical errors are common. Such errors include (1) overgeneralization, (2) false analogy, (3) appeal to authority, (4) arguing in circles, and (5) attack on character.
Overgeneralization, also known as hasty generalization, takes place when we reach a conclusion that goes substantially beyond the facts that inspire it.
Nelson owns stock in ten different companies. The prices on two of his stocks decline by 40 percent. He begins telling friends, “I think there’s going to be another Great Depression.” Melinda’s husband, Clark, forgets their wedding anniversary. The next day Melinda is on the phone telling her best friend, “I don’t think Clark loves me anymore.”
An analogy consists of the observation that two basically dissimilar things have some resemblance to each other. A false analogyexists when the compar- ison between two things is inappropriate. Books on anatomy and physiology often point out that the eye is like a camera. The eye has a lens like a camera. The film in the camera is like the retina; they are both light sensitive. The lens of a camera produces an inverted image on the film; the lens of the eye produces an inverted image on the retina. The eye-camera analogy is a useful one. On the other hand, let’s say that Colby, who grew up on a ranch, compares his car to a horse. “The darn thing gets balky like a horse. Feeding it gas is like feeding a horse hay. It’s get- ting old the way horses do.” However, if one day we hear that Colby in a fit of anger shot the car because the darn thing refused to run, then we would recog- nize that Colby was employing a false analogy.
(a) What kind of logical error takes place when we reach a conclusion that goes substan- tially beyond the facts that inspire it?
(b) What kind of a logical error takes place when the comparison between two things is inappropriate?
Answers: (a) Overgeneralization (or hasty generalization); (b) False analogy.
Appeal to authority is characterized making by a reference to a respected person, believed to be well informed, when one’s own logic or reasoning is weak.
Nadine tells her friend Kitty, who eats no green vegetables, that she should eat more broccoli, peas, and spinach. Kitty asks, “Why?” Nadine says, “Because Dr. Genius says so in his bookGreen Food for a Green Mind.” Although Dr. Genius may know
what he’s talking about, in some cases an authority may be a pseudo-authority or give bad advice. It would have been far better if Nadine could have answered Kitty by saying, “Green foods contain folic acid, an important component of good nutri- tion. Also, vegetables have a lot of fiber, and this promotes regularity.”
Arguing in circles takes place when one’s premise contains the conclusion that one wants to reach. Edgar tells his girlfriend Janet, “I love you.” Janet asks,
“Why do you love me?” Edgar says, “I don’t know. Just because I do.” Janet presses. “But whydo you?” Edgar, sweating and a little confused, says, “Because you’re so lovable!” It would have been a better answer if Edgar could have said,
“Because I like your personality and your sense of humor.” Or, “Because you’re more fun to be with than anyone I’ve ever met.” His actual answer, based on a cir- cular argument, was empty of any real meaning.
Attack on character picks out a negative attribute of another person and uses this attribute to discredit other aspects of the person’s behavior. Kathleen is thinking about taking her car for repairs to Jake, a local auto mechanic. Mabel, a friend, tells Kathleen that she shouldn’t take her car to Jake. “Why?” asks Kath- leen. “Because I hear he cheats on his wife,” says Mabel. Obviously, Jake’s mari- tal behavior has nothing to do with his ability to repair cars.
(a) Making a reference to a respected person, believed to be well informed, when one’s own logic or reasoning is weak is called .
(b) What logical error takes place when one’s premise contains the conclusion that one wants to reach?
(c) What logical error picks out a negative attribute of another person?
Answers: (a) appeal to authority; (b) Arguing in circles; (c) Attack on character.