Expanded Notes on PPAs
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Four broad argument categories dominate the PPA
landscape: inductive arguments, abductive arguments, arguments
by analogy, and confirmation arguments. Here are
thumbnail sketches of each of these, with examples and a description of
the standards that distinguish good examples from bad:
-
Inductive Arguments: The conclusions of
these arguments are generalizations from similar observations or
other similar data points, which serve as reasons.
-
Abductive Arguments: The reasons in
these arguments present clues, often widely disparate, and the
conclusion is the "best explanation" available for these
clues.
-
Arguments by Analogy: The conclusion about
one issue is supported by reasons the point out how a different but
structurally similar issue generates a similar conclusion.
-
Example: My friend argues that he takes
good care of his dog, feeding him, walking him, taking him to
the vet regularly. Thus, he says, he will make a good
parent when the time comes.
-
Standards:
- Plausibility: The more plausible the
story, the stronger the argument.
- Structural Similarity: The more
structurally similar the story in an analogy is to the
topic, the stronger the argument formed around this analogy
will be.
- Inferential Strength: The more closely connected
the conclusion about the story is to the shared structural
elements, the more closely connected the desired conclusion
will be to the topic.
-
Confirmation Arguments: In these, you derive
a hypothesis from your theory and then test it; if the observations
you make support your hypothesis, then it counts as a confirmed
conclusion.
-
Example: If exposure to the sun causes
skin cancer, then we should find a higher incidence of skin
cancer among those who spend a great deal of time in the sun; we
do fin an increased incidence of skin cancer among this
population; therefore, exposure to the sun must cause skin
cancer.
-
Standards:
- Strength of Implication: The stronger the
connection between background claims and implied hypothesis,
the greater the degree of confirmation afforded the
background claim given the truth of the hypothesis.
- Experimental Certainty: The argument will only be
as strong as the degree of certainty associated with the
truth value of the hypothesis.
- Strength of Conclusion: The more a confirmation
argument is asked to confirm, the weaker the confirmation
supplied.
For more detail on all of these, see Chapter
Six, Section III.3 of the UI
Critical Thinking Handbook.
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