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Deductive Reasoning. By: Taylor Bruns. Definition. Deductive reasoning is the opposite of inductive reasoning Noun; reasoning from the general to the particular (or from cause to effect)
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Deductive Reasoning By: Taylor Bruns
Definition • Deductive reasoning is the opposite of inductive reasoning • Noun; reasoning from the general to the particular (or from cause to effect) • Observance of an event occurring on a repeated basis that leads one to believe that a certain probability is attached to the occurrence of that event • Example: A is equal to B. B is equal to C. So, therefore, A is equal to C.
Process • It’s an analytical process that: • 1) takes generally accepted conclusions and • 2) applies them to specific instances to demonstrate that • 3) the conclusion does indeed apply to the specific instance • Example: • 1) All humans are mortal (accepted conclusion) • 2) Socrates is human (applied to a specific instance) • 3) So therefore, Socrates is mortal (conclusion applies to specific instance)
Example • From the reading: • Susan B. Anthony voted before women had been lawfully able to vote. She claimed she did nothing illegal because: • 1) In the preamble of the Constitution, it states that “We the people of the United States” (have such liberties as voting) • 2) She is a person of the United States • 3) So, therefore, she has the right to such liberties as voting
Exceptions • To apply deductive reasoning, the conclusion must be true of any member of a particular class • Since there are exceptions to every rule, be sure to use qualified terms when reasoning deductively • Qualified terms include: most, many, and often • Words to stay away from: all, never, and always
Tests for Deductive Reasoning • Just like there are tests for evidence, there are tests for reasoning as well • Deductive reasoning must be tested two ways • The first thing to test is that the generalization is be true • The second thing to consider is if the generalization applies to the particular case • Generalization – accepted conclusion
First Test • If the generalization isn’t true, then the whole reasoning process is illogical • Example • If someone makes the generalization that people with small, beady eyes are untrustworthy, and then judges a person’s trustworthiness on this basis, then that would not be a valid conclusion • Not all people with small, beady eyes are untrustworthy • http://www.youtube.com/watch?v=YJyuy4B2aKU&feature=PlayList&p=10BB4E7226CB3135&playnext=1&playnext_from=PL&index=33
Second Test • You must ask if the particular case you’re concerned with is similar in all respects to other cases that the generalization applies too • Example: • 1) Democrats raise taxes • 2) This politician is a Democrat • 3) So, therefore, he will raise taxes • Although research can be done to show that most Democrats do raise taxes, if this one in particular has been show to be conservative on that issue, then the reasoning is not correct
Quiz!!! • 1) What words are considered qualifying words when reasoning deductively? (three of the six are correct) • Most Always All Many Never Often • 2) What are the three steps in the process of deductive reasoning? • 3) What are the two tests to spot a failed attempt at deductive reasoning?
Answers!!! • 1) most, many, often • 2) Analytical process: • 1) takes generally accepted conclusions and • 2) applies them to specific instances to demonstrate that • 3) the conclusion does indeed apply to the specific instance • 3) Ask the questions: • 1) Is the generalization true or false? • 2) Does this generalization apply in this specific case?
