Critical Task 3 Rubric Critical Elements Exemplary (1.docx

Critical Task 3 Rubric
Critical Elements Exemplary (100%) Proficient (85%) Needs
Improvement (55%) Not Evident (0%) Value
Main Elements Includes all of the main
elements and requirements
and cites ample appropriate
support to illustrate each
element
Includes most of the main
and cites appropriate support
to illustrate each element
Includes some of the main
Does not include any of the
main elements and
requirements
25
Inquiry and Analysis Explores multiple reasons and
offers accurate and in-depth
analysis of the argument in its
structural form

Explores some reasons and
offers somewhat accurate and
somewhat in-depth analysis of
the argument in its structural
form
Explores minimal reasons and
offers minimally accurate
analysis of the argument in its
structural form
Does not explore reasons and
analysis of evidence and does
not offer accurate analysis of
the argument in its structural
form
25
Integration and
Application
All of the course concepts are
correctly applied
Most of the course concepts
are correctly applied
Some of the course concepts
are correctly applied
Does not correctly apply any of
the course concepts
10

Critical Thinking Demonstrates comprehensive
exploration of issues and ideas
before accepting or forming an
opinion or conclusion about
the argument
Demonstrates moderate
the argument
Demonstrates minimal
the argument
Does not demonstrate
the argument
20
Reflection and
Research
Incorporates a highly pertinent
life goal or issue of significant
importance
Incorporates a life goal or issue
of somewhat significant
importance

Incorporates a life goal or issue
of minimally significant
importance
Does not incorporate a life goal
or issue of significant
importance
10
Writing
(Mechanics/Citations)
No errors related to
organization, grammar and
style, and citations
Minor errors related to
Some errors related to
Major errors related to
10
Earned Total 100%

HYPOTHETICAL SYLLOGISMS
Hypothetical thinking involves “If . . . then . . .” reasoning.
According to some psychologists, the mental model for
hypothetical thinking is built into our brain and enables us to
understand rules and predict the consequences of our actions.
We’ll be looking at the use of hypothetical reasoning in ethics
in greater depth in Chapter 9. Hypothetical arguments are also a
basic building block of computer programs.
A hypothetical syllogism is a form of deductive argument that
contains two premises, at least one of which is a hypothetical or
conditional “if . . . then” statement.
Hypothetical syllogisms fall into three basic patterns: modus
ponens (affirming the antecedent), modus tollens (denying the
consequent), and chain arguments.
Modus Ponens
In a modus ponens argument, there is one conditional premise, a
second premise that states that the antecedent, or if part, of the
first premise is true, and a conclusion that asserts the truth of
the consequent, or the then part, of the first premise. For
example:
Premise 1: If I get this raise at work, then I can pay off my
credit-card bill.
Premise 2: I got the raise at work.
Conclusion: Therefore, I can pay off my credit-card bill.
A valid modus ponens argument, like the one above, takes the
following form:
If A (antecedent), then B (consequent).
A.
Therefore, B.
Sometimes the term then is omitted from the consequent, or
second, part of the conditional premise:
If the hurricane hits the Florida Keys, we should evacuate.
The hurricane is hitting the Florida Keys.
Therefore, we should evacuate.
Modus ponens is a valid form of deductive reasoning no matter

what terms we substitute for A and B. In other words, if the
premises are true, then the conclusion must be true. Thus:
If Barack Obama is president, then he was born in the United
States.
Barack Obama is president.
Therefore, he was born in the United States. C
In this case, the first premise is true because the U.S.
Constitution requires that the president be “a natural born
citizen.” Therefore, the argument is a sound argument.
It is important not to deviate from this form in a modus ponens
argument. If the second premise affirms the consequent (B)
rather than the antecedent (A), the argument is invalid and the
conclusion may be false, even though the premises are true.
If Oprah Winfrey is president, then she was born in the United
States.
Oprah Winfrey was born in the United States.
Therefore, Oprah Winfrey is president.
But of course, as we all know, Oprah Winfrey is not president
of the United States. This deviation from the correct form of
modus ponens is known as the fallacy of affirming the
consequent.
Modus Tollens
In a modus tollens argument, the second premise denies the
consequent, and the conclusion denies the truth of the
antecedent:
If A (antecedent), then B (consequent).
Not B.
Therefore, not A.
Here is an example of a modus tollens argument:
If Morgan is a physician, then she has graduated from college.
Morgan did not graduate from college.
Therefore, Morgan is not a physician.
Like modus ponens, modus tollens is a valid form of deductive
reasoning. No matter what terms we substitute for the
antecedent (A) and consequent (B), if the premises are true,
then the conclusion must be true. If we change the form by

changing the first premise to read “If not A, then B,” we
commit the fallacy of denying the antecedent.
Chain Arguments
Chain arguments are made up of three conditional
propositions—two premises and one conclusion— linked
together. A chain argument is a type of imperfect hypothetical
syllogism since it may contain more than three propositions.
If A, then B.
f B, then C.
Therefore, if A, then C.
The following is an example of a chain argument:
If it rains tomorrow, then the beach party is canceled.
If the beach party is canceled, we’re having a party at Rachel’s
house.
Therefore, if it rains tomorrow, we’re having a party at Rachel’s
house.
Just as some arguments by elimination are syllogisms and others
are not, we can have a longer chain argument that is still a
deductive argument but not a syllogism because it has more than
two premises. For example:
If A, then B.
If B, then C.
If C, then D.
Therefore, if A, then D.
Here is an example of a chain argument with three premises:
If you don’t go to class, you won’t pass the final exam.
If you don’t pass the final exam, then you won’t pass the
course.
If you don’t pass the course, then you won’t graduate this year.
Therefore, if you don’t go to class, you won’t graduate this
year.
A chain argument is valid if it follows the form of using the
consequent of the previous premise as the antecedent in the next
premise, and so on, with the conclusion using the antecedent
from the first premise (A) and the consequent in the last
premise (D).

Glossary:
hypothetical syllogism: A deductive argument that contains two
premises, at least one of which is a conditional statement.
modus ponens: A hypothetical syllogism in which the
antecedent premise is affirmed by the consequent premise.
modus Tollens: A hypothetical syllogism in which the
antecedent premise is denied by the consequent premise.
chain arguments: A type of imperfect hypothetical argument
with three or more conditional propositions linked together.
Evaluating Hypothetical Syllogisms for Validity
Not all hypothetical syllogisms are laid out in standard
syllogistic form. If an argument isn’t already in standard form,
put it in standard form with the conditional premise first and the
conclusion last. In the case of a chain argument, begin by
listing the premise containing the antecedent from the
conclusion. In 1758, Ben Franklin offered this bit of wisdom in
his famous Poor Richard’s Almanac: For want of a Nail the
Shoe was lost; For want of a Shoe the Horse was lost; For want
of a Horse, the Rider was lost, being overtaken and slain by the
enemy; For want of Care about the Horse-Shoe Nail, the Rider
is lost. Let’s test the validity of Franklin’s argument by writing
it out as a hypothetical syllogism, in this case a chain argument:
If a nail is missing (A), then the horseshoe will be lost (B).
If the horseshoe is lost (B), then the rider is lost (C).
If the nail is missing (A), then the rider is lost (C).
By rewriting this as a hypothetical syllogism, we can see that it
is a valid argument. In some cases, it may be too awkward to
restate each use of the antecedents and consequents using the
exact same language as in Franklin’s argument. In these cases,
it is acceptable to use everyday language as long as the meaning
remains the same each time it is used. Otherwise, the argument
commits the fallacy of equivocation.
A hypothetical syllogism is valid if it follows one of the forms
discussed in this chapter—modus ponens, modus tollens, or
chain argument. If you are uncertain whether a hypothetical

syllogism is valid, you can also try substituting different terms
for those used in the argument under evaluation.
Not all valid arguments are sound. As we noted earlier, a
deductive argument can be valid by virtue of its form but still
be unsound because one of the premises is false. Rewording
arguments in ordinary language in the form of a hypothetical
syllogism can help you expose the faulty premises. Suppose you
are looking for a new cell phone and find two models that seem
to suit your needs—a Sony and a Motorola. Both have similar
features, but the Sony costs more than the Motorola. So you
think: The Sony cell phone costs more, so it should be the better
phone. I think I’ll buy the Sony. Putting your argument in the
form of a hypothetical syllogism, we have this:
If a product is expensive, then it must be good.
This brand of cell phone is expensive.
Therefore, it must be good.
However, the first premise is false. Not all expensive products
are good, nor are all inexpensive products of poor quality.
Therefore, this is an unsound argument. Unfortunately, many
people fall for this line of reasoning. Indeed, some clever
marketers have found that when they increase the price of
certain items, such as jewelry or clothing, it actually sells
better!
Putting an argument in the form of a hypothetical syllogism can
be helpful in clarifying what’s at stake. Consider this argument
from the abortion debate:
If a being is a person (A), then it is morally wrong to kill that
being except in self-defense (B).
The fetus is a person (A).
Therefore, it is morally wrong to kill the fetus except in self-
defense (B).
HIGHLIGHTS

VALID FORMS OF HYPOTHETICAL SYLLOGISMS
Modus Ponens
Modus Tollens
Chain Argument
If A, then B.
If A, then B.
If A, then B.
A.
Not B.
If B, then C.
Therefore, B.
Therefore, not A.
Therefore, if A, then C.
Judith Jarvis Thomson, in her essay “A Defense of Abortion”
(which we will read at the end of Chapter 9), recognizes the
strength of this type of deductive reasoning and acknowledges
that she must accept the conclusion if she accepts the premises
as true. She also realizes that the only way to reject this
argument—since it is a valid argument—is to show that one of
the premises is false and therefore the argument is unsound.
Otherwise, she must accept the conclusion. Since she can’t
prove that the fetus is not a person, she tentatively accepts the
second premise as true. Instead, she questions the first premise,
arguing that there may be circumstances when we can kill
another person for reasons other than self-defense.
Hypothetical arguments are common in everyday reasoning. In
addition to being used in promises and ultima- tums (see
“Critical Thinking in Action: Empty Promises: If This, Then
That—Making Promises and Threats” on page 249), they can be
used to spell out the outcomes of certain choices you make in
your life: for example, the necessary antecedents you’ll need to
graduate from college or go on graduate school.
Exercise 8-3

#3. Think of an issue or goal that is important in your life.
Write a hypothetical syllogism related to the issue or goal.
Evaluate the syllogism for validity and soundness.

Critical Task 3 Rubric Critical Elements Exemplary (1.docx

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