1. Revisiting the Toulmin Model and its Greek Predecessors
Errors in Reasoning:
Revisiting the Toulmin Model and its Greek Predecessors

2. The Core Concepts
To detect errors in argumentation… Ask probing questions that politely but relentlessly demand… Logical Consistency Corroborated Evidence

3. A Corny Ode to Toulmin: “The Model Model”
Deliberately designed With these core concepts in mind, To be as error free As any argument can be With data and warrants and qualifiers, too It seems the perfect argument For me and for you

4. Self-Checks in Picture Form

5. Self-Checks in Words The Data generates the Claim.
The Backing justifies the Warrant, which
justifies the Claim.
The conditions of Rebuttal determine the
Qualifier, realistically limiting the scope of the
Claim.

6. However, one can still ask…
Does the data prove the claim? Does the qualifier sufficiently limit the claim? Does the warrant justify the claim? Is there a better warrant to justify the claim? Does the backing justify the warrant?

7. And what about that data?
Is it directly relevant to the claim? Is it sufficient to prove the claim? Are its sources trustworthy? Are its methodologies reliable? Is it up-to-date?

8. Any answer that is a no…
does not necessarily invalidate the entire argument, though it may
does indicate an error in reasoning, which may slightly, moderately, or severely weaken
the argument, depending on the severity of the error

9. What about the Greeks? Deduction Induction Major Premise Minor Premise
Conclusion
Induction
Generalization
Cause-Effect
Analogy

10. More Internal Self-Checks to Ward off Errors and Weaknesses
Toulmin vs. Aristotle
More Internal Self-Checks to Ward off Errors and Weaknesses
More External
Checks to
Analyze Logic
and Find
Weaknesses

11. External Checks Deduction Induction Is the argument valid?
Is the argument sound?
Because deduction is a conclusive form of reasoning, the tests are likewise conclusive (i.e. either valid or invalid).
Induction
Is the argument strong?
Is the argument cogent?
Because induction is based on probable outcomes, the results of the tests are not absolute but differ in degree.

12. Evaluating Deductive Arguments I
A deductive argument is valid if the conclusion
follows from the premises regardless of the
truth of the premises or conclusion.
All cheetahs have purple eyes.
Frita is a cheetah.
Therefore, Frita has purple eyes.

13. Evaluating Deductive Arguments II
A deductive argument is invalid if the conclusion
does not follow from the premises regardless of
the truth of the premises or conclusion.
If Alexander Hamilton died of heart disease, then
Hamilton is dead today.
Hamilton is dead.
Therefore, Hamilton died of heart disease.

14. Evaluating Deductive Arguments III
A deductive argument is sound if it is valid
and all of the premises are true.
All men are mortal.
Socrates was a man.
Therefore, Socrates was mortal.

15. Evaluating Deductive Arguments IV
A deductive argument is unsound if any part of it is false regardless of whether or not the argument is valid. The doctor is a groundhog. All groundhogs are mortal. Therefore, the doctor is mortal.

16. More Practice with Deduction
All bears eat oysters All bears have fur.
Julian is a bear Julian is a bear.
Therefore, Julian eats oysters Therefore, Julian has fur.
All people are mortal The fridge always cooks Julian (the bear) is mortal meat.
Therefore, Julian is a person. The chicken is in the fridge.
Therefore, the chicken is
cooking.

17. Answers
1. valid, unsound 2. valid, sound 3. invalid, unsound 4. valid, unsound

18. Evaluating Inductive Arguments I
An inductive argument is strong if the conclusion
is probably true (50% chance or higher)
regardless of whether or not the premises are
true .
Most boys like to play sports.
Britney Spears is a boy.
Therefore, Britney probably likes to play sports.
(Example from

19. Evaluating Inductive Arguments II
An inductive argument is weak if the conclusion
is probably false (50% chance or higher)
regardless of whether or not the premises are
true.
Grass is green.
Spinach is green.
Spinach and grass probably taste the same.
(Example from Shabo, Magedah. Rhetoric, Logic, and Argumentation: A Guide for Student Writers. Prestwick, 2010.)

20. Evaluating Inductive Arguments III
An inductive argument is cogent if the premises
are true and the conclusion
is probably true (50% chance or higher).
Most recording artists have talent.
Britney Spears is a recording artist.
Therefore, Britney probably has talent.
(Example from

21. Evaluating Inductive Arguments IV
An inductive argument cannot be cogent unless
the premises are true and the conclusion is
probably true (50% chance or higher);
otherwise, it is uncogent (or not cogent).
The average human body temp. is 55 deg. F.
My current temperature is 102 deg. F.
I probably have a fever.
(Example from Shabo, Magedah. Rhetoric, Logic, and Argumentation: A Guide for Student Writers. Prestwick, 2010.)

22. More Practice with Induction
This jar contains 30 pieces
of candy.
25 randomly selected pieces
are M&Ms.
Probably, all the pieces are
M&Ms.
3. The constellations are
frozen humans and animals.
The sun is hot.
The sun could melt the
constellations.
2. This jar contains 30 pieces
of candy.
5 randomly selected pieces
are M&Ms.
Probably, all the pieces are
M&Ms.
Most pumpkins are orange.
Most oranges are orange.
Pumpkins taste like oranges.

23. Answers
1. strong, cogent 2. weak, uncogent 3. strong, uncogent 4. weak, uncogent

24. A Range of Imperfections
As should be clear by now, arguments can be flawed or imperfect in a number of ways, depending on the type of argument:
Toulmin Weak Links between Parts
Weaknesses in the Data
Deduction Invalidity, Unsoundness
Induction Weakness, Un-cogency

25. Worse than Weak outrageous errors in argumentation
Somewhat ironically, the most
outrageous errors in argumentation
(yet to be studied in this course) recur so
frequently they have each been given
their own name.
Collectively, they are called the logical
fallacies.

26. Not Every Weakness is a Fallacy
For example,
An analogy (the third type of induction) would
be considered weak if less than 50% of the
analogy applied to the argument.
An analogy would have to be extremely weak to
be classified as a fallacy of a false analogy.

27. On the Other Hand…
Sometimes a mistake is almost always classified as a
fallacy.
For example, flaws in linking causes and effects (the
second type of induction) would almost always be
categorized as the fallacy of correlation versus causation.
Most of the time, however, there is a wide range of
imperfection, all the way from minor flaw to full-
blown fallacy.

28. Much more to come on fallacies in Lesson 8!
Preview
Much more to come on fallacies in Lesson 8!

29. A Review of Ranges a range of intentionality, all the way from
In addition to a range of errors, there is also
a range of intentionality, all the way from
absolutely unintentional to entirely
deliberate.
There are just so many ways for human
beings to be imperfect.

30. A “Philosophy” of Flaws
Thus, as the saying goes, “To err is
human, to forgive divine.”
Or should we say: as it is human to err, it
is thus critical to critique—our entire focus
in this unit!