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Critical Thinking. “The Art of Reasoning Well”. Critical Thinking. Reasoning Well Involves Arguments. Argument does not mean a verbal dispute. An Argument Is A Series Of Statements, Called Premises, Leading To A Conclusion. Logic: The study of the formal principles of reasoning. Arguments.
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Critical Thinking “The Art of Reasoning Well”
Reasoning Well Involves Arguments • Argument does not mean a verbal dispute
An Argument Is A Series Of Statements, Called Premises, Leading To A Conclusion
Logic:The study of the formal principles of reasoning Arguments
Deductive Argument: the truth of the premises guarantees the truth of the conclusion Inductive Argument: the truth of the premises makes the truth of the conclusion more probable Arguments
Example (Valid): 1. If it snows, then it is cold (premise) 2. It snows (premise) 3. Therefore, it is cold (conclusion) VALID DEDUCTIVE ARGUMENT: The argument is in the proper form Deductive Arguments
Example (Invalid): 1. If it snows, then it is cold (premise) 2. It is cold (premise) 3. Therefore, it snows (conclusion) Deductive Arguments
INVALID : The argument is not in the proper form. Informal testing for deductive validity: Can You Think of a counter example? If yes, the argument is invalid. Deductive Arguments
If Tom Cruise is a bulldog then he has four legs (Premise) Tom Cruise is a bulldog (Premise) Therefore, Tom Cruise has four legs (Conclusion) Is the Argument Valid? Have we proven that Tom Cruise has four legs? Deductive Arguments
Deductive Arguments • If it is determined that the argument is valid it must next be determined if the argument is sound. • A sound argument is valid argument with true premises.
If Tom Cruise is a bulldog then he has four legs Tom Cruise is a bulldog Therefore Tom Cruise has four legs Is the Argument Sound? Deductive Arguments
Inductive Arguments • Examples: • 1.All observed emeralds have been found to be green 2.Therefore, the next observed emerald will be green. • 1.In the past, sugar cubes have dissolved in water 2.Thus, this sugar cube will dissolve in water. • 1. 70% of BCCC students in the sample are from Bristol 2. Hence, 70% of BCCC students are from Bristol
Many times arguments have one or more unstated premises that need to be added to support the conclusion. Sally’s dog is a bloodhound therefore it has a keen sense of smell Unstated Premises
It is February, so I will dress warmly Drugs should not be legalized Unstated Premises
Analyzing Arguments Reconstruct the Argument • 1. Find the conclusion. • 2. Find the premises • 3. Find any unstated premises
Conclusion: Defendant should be acquitted Premise(s): The glove doesn't fit the defendant (premise - stated) Unstated premises: If evidence does not fit the defendant, then the defendant should be acquitted (premise - unstated) The glove is evidence (premise - unstated) “The glove doesn’t fit so you must acquit”
Analyzing Arguments • Evaluate the argument • 1. Is the argument valid? • (Can I think of a counter example?) • 2. Are the premises true?
1. Is the argument valid? (Can I think of a counter example?) 2. Are the premises true? If evidence does not fit the defendant, then the defendant should be acquitted The glove is evidence The glove doesn't fit the defendant Therefore, defendant should be acquitted Evaluating the Argument
Logical Fallacies • Mistakes in logic when presenting our arguments. Formal Fallacy: An invalid argument Informal Fallacy: Type of bad reasoning that can only be detected by examining the content of the argument.
Begging the Question Assuming what you are trying to prove “Capital punishment is wrong because it is immoral” Informal Fallacies
Ad Hominem Attack Attack on your opponent rather that his or her argument “The only reason that you think Capital punishment is wrong is because you are a bleeding heart liberal” Informal Fallacies
Red Herring: Sidetracking the argument with an irrelevant issue “Honda makes the best cars” --- “No they don’t their workers are treated poorly” Informal Fallacies
Hasty Generalization: Drawing general conclusions from a small sample “A number of professional athletes have been convicted of crimes therefore all professional athletes are criminals” Informal Fallacies
George bush is a good president George Bush is a bad president Arguments