Chapter 4: The Skills of Reasoning
1. Explain the concept of proof.
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Proof is information entered into a dispute in support of a claim.
To serve as proof, the information offered in support must be relevant and
reliable.
2. Why is it important that an argument be based on evidence?
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Argument cannot advance without evidence.
Evidence offered as proof creates the possibility for agreement.
3. In reasoning by generalization, what are the major types of evidence used? Describe
three tests that help to insure that your generalizations are sound.
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Major types: The example (listing) and specific instance to illustrate a
generalization (details about one)
Three tests:
(1) Are there enough examples?
(2) Are the examples typical of the group?
(3) Are there significant counterexamples?
4. How is reasoning by analogy helpful to someone who is listening to your argument?
Define a false and an extended analogy.
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An arguer can make an unknown claim more certain by comparing it to a
known or accepted claim.
False analogy: points of dissimilarity are greater than points of similarity
Extended analogy: illustrates the offered comparison in detail; helps arguers
evaluate the analogy
5. Most events in forensics deal with reasoning from cause and effect relationships.
Define reasoning based on cause-effect sequences. Provide an example. In your
example, are there any intervening causes?
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A cause-effect relationship is one in which two phenomena (objects, events)
are observed interacting together in some process and it is assumed that one
caused the other.
“I am a better driver because I took driving lessons.”
Intervening factors: causal chain of reasoning is lengthy
6. In the argument “Our school has a great football team and therefore should do well
in city competition because it has lost only two of its last ten games,” what type of
reasoning is used? How could such an argument be challenged?
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Sign argument – based on the evidence that the team is excellent (based on
the sign of excellence)
Past victories do not cause future ones in this case; schedule weak (negates
the sign)
7. What is the value of using statistics to support reasoned conclusions?
 Permits conclusions to be drawn from a large sample population to
determine with some accuracy the characteristics of a groups;
 Permits understanding of interactions where factors interact with one
another;
 Possibility of prediction and control
8. When examining statistics for use as evidence, why is it appropriate to understand
the methodology?
 Qualify and limit the reliability of conclusions
 Can determine what weight the statistics should be given for purposes of
argument
9. Forensic events often use evidence drawn from opinion, testimony, or both. To
support the claim “The United States should maintain a balanced budget,” find two
pieces of evidence that rely on authority. How do your authorities meet tests of
source credibility suggested by rhetorical considerations? Next, apply routine tests
of evidence.
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Consult statements by various politicians from different parties at different
levels of government; opinions of economists; international trade experts, or
stockholders
Explain how opinions are trustworthy (experience and motives of the
persons)
Be able to discount the credibility of those authorities who argue your
position