Elementary
Logic (PHIL-1030 [54007])
Prof.
Edgar
Boedeker Fall
2017 MWF,
12:00-12:50 Lang
20
Office hours: 2:15-3:15pm Tuesdays and Wednesdays in my office,
2099 Bartlett. I would also be happy to meet with you at another time, to be arranged in advance. If you would like to schedule such a
meeting, please contact me in person, by e-mail (edgar.boedeker@uni.edu), or give me a call at
273-7487.
Required Text: Patrick J. Hurley, A Concise Introduction to Logic, Ninth Edition (Wadsworth, 2005; ISBN: 9780534585051),
available at University Book & Supply (1099 W. 23rd St.) and numerous online venues.
Why Study Logic? A brilliant (but rather eccentric) Austrian named Ludwig
Wittgenstein (1889-1951) wrote what is surely the greatest philosophical work
on logic, the 50-page-long Tractatus Logico-Philosophicus. When he was 23 years old, hard at
work on this book, he wrote to his friend and mentor, the logician Bertrand Russell: “Logic must turn out to be of a totally different
kind than any other science.” Soon, he would discover that it is not a
“science” at all – at least not in the way that biology, chemistry, and even
higher mathematics are sciences. That is, logic does not try to make true and
abstract statements about particular kinds of things, such as living things,
molecules, or various kinds of numbers. (Statements, also known as
propositions, beliefs, etc., are whatever is either true or false.) But this does not mean at all that logic is merely
“subjective.” so that I have my logic and you have yours. Rather, logic
occupies an absolutely central place within statements,
and especially within the relations among them. For example,
biology tells us that all whales are mammals, and that no mammals are fish.
From these two statements, we can logically draw the
conclusion, or “infer,” that no whales are fish (and thus that quite a number
of statements in Moby Dick are false).
Logic
occupies a similarly central place in ordinary, everyday speaking and thinking.
For example, if someone tells you that they’ll either study tonight or go to a
movie, and they don’t end up going to a movie tonight, then you can infer – at
least if what they’ve said is true – that they’ll study tonight. Logic examines
these and other kinds of inferential relations among
statements. Indeed, logic (as an academic discipline) can be
defined as the study of inferential relations among statements.
Thus
logic is absolutely central to genuine thinking (as
opposed to merely experiencing sensations or images) and to genuine language
(as opposed to the sort of thing that parrots or newborn infants do). For this
reason, we already understand logic, and have as long as we
have been able to genuinely speak and think. What, then, is the point of studying logic
as an academic discipline?
The
answer is that the “natural” languages we speak, such as English or German, did
not arise solely for the purely logical purpose of making inferences between
some statements and others. Instead, they developed for a host of reasons, many
having to do with convenience and brevity. For such reasons, our languages
sometimes mislead us into inferring some statements that really don’t follow from others, even though they might seem to.
Essentially, the point of studying
logic is to make us aware of these kinds of errors. This helps us in three
ways. First, the study of logic can help us avoid errors in our own thinking,
so that we can come to make only those inferences that really do follow from
what we believe. Second, logic can help us be clearer when we present our
thoughts, in speech or in writing, to others. Third, and perhaps most
importantly, studying logic can help us to avoid being swayed by people who –
whether they know it or not – try to persuade us to accept some conclusion that
really doesn’t follow from what we know to be true. In
this way, studying logic can help make us sharper, more critical readers,
thinkers, and citizens.
Course Content: This course will introduce you to different formal and
informal methods of analyzing, symbolizing, and evaluating arguments. Topics
covered will include sentence logic, basic predicate logic, and informal
fallacies.
Course Format: Class meetings will consist of lecture, questions,
discussion, and quizzes. Also be aware that there will
be a lot of homework for this class!
Grading: Your final grade will be determined as follows:
1. There will be about 12 quizzes, each worth about 5% of your
total grade, for a total of exactly 60% of your final
grade.
2. The assigned homework will be worth a total
of 40% of your final grade. The homework due since the last quiz will be accepted only in class at
the beginning of the class meeting on the day on which it is due. Homework will
be graded with a “check” (full credit: 100%), “check/check-minus” (75% credit),
“check-minus” (half credit), “check-plus” (credit-and-a-half), or
“check/check-plus” (125% credit) based on the perception of your good-faith
effort in completing it. To save some time, I’d
recommend typing the assignments at the beginning and conclusion of the
semester, since they involve just text in ordinary English; and handwriting the
rest of the assignments, which involve logical symbols or diagrams.
3. You will have the opportunity to make up between two and four
quizzes of your choice. I’ll announce the exact number
of quizzes during the last week of the semester. These can be either quizzes
that you missed or ones on which you’d like to improve
your score. The make-up quizzes will be graded on a
“no penalty” basis. That is, if your grade on the make-up quiz differs from
that on the original quiz for the corresponding week, only the higher of the
two grades will be counted. Naturally, the make-up
quizzes will be different from the quiz given in class of the corresponding
week, although they will cover roughly the same material. I plan to hold the
make-up session on our last regular class meeting; please see the end
of the syllabus for more on the make-up sessions. But if it turns out that we get sufficiently behind schedule
by the end of the semester, then the make-up session will be held in our
regular classroom at our officially-scheduled final exam time; Please
see the very bottom of the syllabus for the date and time. I
plan to let you know the date of the make-up session the Monday of the last day
of classes.
Please don’t text
on an electronic device, wear headphones, etc. I’ve
found that the use of such devices is very distracting to me, reduces my
ability to teach effectively, and hence does a disservice to the students in
the class. In addition, some folks need a bit of practice in
breaking the habit of feeling the need to text during inappropriate
times. Thus if you do this, I will have to ask you to leave class.
4. Attendance: I reserve the right to
take attendance at the beginning of each class period. You are permitted two unexcused absences
during the semester. For each unexcused absence beyond these two,
your final grade will be reduced by one third of a
letter grade. For example, someone with a B+ average with 4 unexplained absences (i.e., 2 more than the 2 allowed) will
receive a B- in the course. Although I’d
appreciate it if you inform me prior to class that you’ll be absent, not all
announced absences will count as excused. The only excuses I will accept are a
weather emergency, illness documented by doctor’s note, documented funeral,
documented mandatory participation in UNI athletics, or documented military
service.
I realize that this is a fairly strict
attendance policy. I have instituted it mainly because much of the
learning that you will do in this course will take place in
class. Asking questions, raising objections, and listening to others
are important skills that you will get to practice in class
discussions. In addition, coming to class is necessary to doing well
in this course. Finally, if you initiate class discussion on a given
topic, this will aid others in coming to terms with the material covered.
Further note: Each semester, I teach almost 100 students. Although I give
you as much individual time and attention as I possibly can during the
semester, I will not be able to send you your individual grade for the course
at the end of the semester. I submit the grades to the Registrar as soon as I
can during the week of final exams, and ask you to kindly
wait to see your grade until it has been reported electronically.
Website: Helpful handouts to supplement the textbook are linked to my teaching website: http://www.uni.edu/boedeker. Please print these out and read them.
MAILSERV: From time to time, I will send announcements pertaining to the class via
e-mail. To facilitate our electronic communication, a MAILSERV
distribution list has been created for this class using your UNI e-mail addresses. It
will be your responsibility to check your e-mail regularly, read the
announcements, and print out all attachments. You
might want to purchase a 3-ring binder to organize and store the various
handouts for this class.
Cheating and plagiarism: It is your responsibility to read UNI’s Student Academic Ethics Policy (Chapter 3.01 of UNI’s Policies and Procedures Manual, available at https://www.uni.edu/policies/301). Using the terminology defined in this document, please
note the following:
Any student who commits a Level One
violation will receive no credit
for the entire assignment in question.
Any student who commits a Level Two violation will receive no credit for the entire assignment
in question; and, in addition, a reduction in the course grade
by two full letter grades, i.e., 20% (e.g., from a B- to a D-).
Any student who
commits a Level Three violation is mandated by the
University to receive a disciplinary failure for the course. (This will
automatically appear on the student’s transcript.) As your
professor, UNI also requires me to reprimand the student in writing in the form
of a letter addressed to the student and copied to the Head of the Department
of Philosophy and World Religions, the student’s department head (if different)
and the Office of the Executive Vice President and Provost.
Disabilities: Please contact me if I can be of assistance in this area. All
qualified students with disabilities are protected under the provisions of the
Americans with Disabilities Act (ADA), 42 U.S.C.A., Section
12101. The ADA states that “no qualified individual
with a disability shall, by reason of such disability, be excluded from
participation in or be denied the benefits of the services, programs or
activities of a public entity, or be subjected to discrimination by any such
entity.” Students who desire or need instructional accommodations or assistance
because of their disability should contact the office of Student
Disability Services, located in 103 Student Health
Center (voice: 319-273-2677; for deaf or hard-of-hearing, use Relay 711).
Tentative Course Schedule:
The assignments are due in
class on the date indicated.
General note on the homework assignments: The answers to all exercises marked with a star are given at the back of the book. Unless I specifically ask
you to in a particular homework assignment, I won’t
require that you complete any of these exercises. Nevertheless, you’re welcome to do so if you feel that you could use some
extra practice.
Note on
opening handouts: Sometimes, when using Google Chrome
to open an attached document, the default will be to open it as a google doc.
When this happens, special characters, such as our logical operators, will come
out wrong (often, I've seen, as parentheses). To make
sure you're opening the document as it should be, I've
found the following trick to work:
1. Right click (not left click) on the link.
2. Select "Save link as..."
3. When a default file name appears, hit "Save"; the
file name should appear in the bottom left-hand corner of your screen.
4. Click on the file name, and the document in the proper format
should appear; this is the one to print out.
I. Some Basic Logical Concepts:
21 Aug.: Introduction.
23 Aug.: Read section 1.1 and this handout. Do exercises 1.1: I: 1-30 and II: 1-10. Please note
that on this assignment, as well as others throughout the semester, you should
feel free to use ellipses “[…]” to abbreviate longer sentences; do make it
clear exactly which sentence you’re indicating,
however, by including its first and last couple of words. Do not
include premise or conclusion indicator words (e.g., “since.” “therefore,” etc.) in your premises
or conclusions; such words only serve to indicate that what
follows is a premise or conclusion, but are not part of these
statements.
25 Aug.: Read section 1.2, but only pp. 14-15,
on arguments; and pp. 19-23, on explanations and conditional statements; also
read this handout. Do exercises 1.2: I:
1-35. Since explanations and conditional statements are the only
kinds of passages we’ve dealt with that don’t contain arguments, change the third
sentence of the instructions (p. 23) to the following: “For those that are not,
write, where appropriate, either ‘Explanation’ (stating the explanandum, i.e., the statement explained);
‘Conditional statement’; or ‘Other non-argumentative passage.’”
28 Aug.: Do exercises 1.2: II: 1-10 and
VI: 1-10.
II. Propositional Logic:
30 Aug.: Read section 6.1, this handout, and this handout. Do exercises 6.1: I: 1-25,
including those exercises marked with an “*”.
1 Sept.: Do exercises 6.1: I: 26-50,
including those exercises marked with an “*”.
6 Sept.: Do exercises 6.1: II: 1-20
and III: 1-10.
8 Sept.: Read section 6.2. Do exercises 6.2:
I: 1-10.
11 Sept.: Do
exercises 6.2: II: 1-15, III: 1-25, and IV: 1-15.
13 Sept.: Read section 6.3, this handout, and this handout. Do exercises 6.3: I: 1-13 and II:
1-15.
15 Sept.: Do exercises 6.3: III:
1-10, including the exercises marked with a star.
18 Sept.: catch-up day.
20 Sept.: Read section 6.4 and this handout. Do exercises 6.4: I: 1-7 and 9; and 6.4: II: 1-7. Change the instructions in 6.5: I to
“Determine whether the following symbolized arguments are valid or invalid by
constructing a truth table for each,” and do exercises 6.5: I: 1, 2, and 4.
22 Sept.: Read
section 6.5. Change the instructions in 6.3: I to “Use indirect truth-tables to determine
whether the following symbolized statements are tautologous,
self-contradictory, or contingent,” and do exercises 6.3:
I: 14 and 15. (Hint for exercise 14:
Since this is a conditional statement and there’s only
one combination of truth-values under which a conditional statement is false,
try to make it false; if this proves impossible, then the statement is a
tautology. Exercise 15 is quite
challenging; give it a try but don’t spend too much
time on it.) Change the instructions in 6.4:
I and 6.4: II to “Use indirect truth-tables
to determine whether the following arguments are valid or invalid,” and do
exercises 6.4: I: 8 and 10, and 6.4:
II: 8-20. (You’ll see that using indirect truth-tables
will save you a lot of “busy work” here.) Do exercises 6.5: I: 3,
5-8, and 11-13; and exercises 6.5: II: 1-3 and 6-8.
25 Sept.: Change the instructions
in 1.5: II to “Use indirect truth-tables to determine
whether the following arguments are valid or invalid,” and do exercises 1.5:
II: 1, 2, 3, 4, including those exercises marked with
a star.
27 Sept.: Read section 6.6, the summary
on pp. 336-7, and this handout. Do exercises 6.6:
I: 1-20. Please note that the last sentence of the instructions for 6.6: I is
misleading, since it’s not the case
that all arguments without a named form (modus ponens, modus tollens, etc.) are invalid. That is, some arguments
without a named form are valid.
29 Sept.: Do exercises 6.6: II:
1-20. Please note that the last sentence of the instructions for 6.6: II is
misleading, for the same reason as was mentioned in the previous assignment.
Also do exercises 6.6: III: 1-10 and IV: 1-10.
2 Oct.: catch-up day.
III. Predicate Logic:
4 Oct: Read section 8.1, this handout, and this handout. Do exercises 8.1: 1-30, including
those exercises marked with a star.
6 Oct.: Do exercises 8.1: 31-60,
including those exercises marked with a star.
9 Oct.: Read section 4.7
and this handout. Change the instructions
in 4.7: I to “Express the following statements in
predicate logic,” and do exercises 4.7: I: 1-30. Please use just two predicate-letters to express
each proposition. In some cases, this will involve combining more than one
concept into a single predicate. Feel free to make up your own
predicate-letters or to use the predicate-letters in this homework
help. Also
make sure to save this homework assignment, as you’ll be
referring to it later.
11 Oct.: Do exercises 4.7: I: 31-60,
using the same instructions as in the previous assignment and the predicate
letters given in this homework help. Make sure to save this
homework assignment, as you’ll be referring to it
later. Also read from p. 411 to the top of p. 412 (at the beginning
of section 8.3), summarized in this handout.
13 Oct.: Use predicate logic to do
exercises 5.7: III: 1-10, including those exercises
marked with a star. You’ll be using the
inference-rules of pure hypothetical syllogism, transposition (which
is close to contraposition), and double negation (look
them up in the index at the back of the book), modified to apply to predicate
logic. Note that in all of the exercises except 1 and
3 you’ll need to specify the “universe of discourse,” i.e., the set of things
that all propositions in the argument are talking about. For example, the
universe of discourse in exercise 2 is persons; the universe of
discourse in exercise 4 is birds; the universe of discourse in
exercise 5 is fruits, etc. Make sure to reduce the number of terms
whenever possible; that is, if two predicates occurring in an argument have
(close to) opposite meanings (e.g., “dances” and “declines to dance”), use a
single predicate and its negation (e.g., “Dx”
and “~Dx”) to express both. (In exercise 6,
use either the predicate “x is a daughter” or “x is a
son,” but not both.)
16 Oct.: catch-up day.
IV. Categorical Propositions
18 Oct.: Read section 4.1. Do exercises 4.1:
1-8. Also read section 4.2, but only p.
186 through the second full paragraph on p. 187. Also
read section 4.3, but only from the bottom of p. 192 (under
“Venn Diagrams”) through the end of 4.3 (on p. 198). Please note that in this
course the only interpretation of categorical logic that we’ll
be using is the “modern,” or “Boolean,” standpoint – not the
ancient and medieval “traditional,” or “Aristotelian,” one. Also do exercises
4.3: I: 1-8.
20 Oct.: Change the instructions in 4.3: II to
“Use Venn diagrams to determine whether the following immediate inferences are
valid or invalid from the Boolean standpoint,” and do exercises 4.3: II: 1-15.
Also change the instructions in 4.5: I to “Use Venn
diagrams to determine whether the following immediate inferences are valid or
invalid from the Boolean standpoint,” and do exercises 4.5:
I: 1-8, including those exercises marked with a star.
In order to do the assignments due this day, use the “modern,” or “Boolean” square of opposition. As
discussed on pp. 196-198, and immediate inference is an
argument with just one statement as its premise and just one statement as its
conclusion. Here’s how it works for the
four forms of categorical propositions discussed so far:
“All S are P” is true if and only if “Some S are not P” is false.
“Some S are not P” is true if and only if “All S are P” is false.
“No S are P” is true if and only if “Some S are P” is false.
“Some S are P” is true if and only if “No S are P” is false.
No other immediate inferences from one of these four standard-form
categorical propositions to another are valid. For example, the
following immediate inference is invalid:
Premise: “All S is P”
Conclusion: “Some S is P”
23 Oct.: In section 4.4,
read just the second and third paragraphs on p. 202 (where “term
complement” is defined), and commit this handout to memory. Also read as much of
this handout as you need to understand the material. Then change the
instructions in 4.4: I to “Ignore the second column. Instead, begin with the statement
and its truth-value given in the first column. The third column provides a new
statement. In the fourth column, supply the truth-value of this new statement when
the first statement has the truth-value given in the first column; your answers
in the fourth column will be either “true,” “false,” or “undetermined.” The new
statements in the third column will be as follows:
1.
No non-B are A.
2.
Some non-B are non-A.
3.
No A are B.
4.
All non-B are A.
5.
Some B are not non-A.
6.
Some non-A are not B.
Change the instructions in 4.4: II to “Supply the truth-value (true,
false, or undetermined) of the new statement when the given statement is true.”
The new statements will be as follows:
1a. All storms intensified by global
warming are hurricanes.
1b. No completely successful procedures are sex-change operations.
1c. Some works that celebrate the revolutionary spirit are
murals by Diego Rivera.
1d. Some substances with a crystalline structure are not forms
of carbon.
2a. No
radically egalitarian societies are societies that preserve individual
liberties.
2b. All
cult leaders are people who brainwash their followers.
2c. Some college football coaches are not people who slip money
to their players.
2d. Some budgetary cutbacks are actions unfair to the poor.
3a. All physicians eligible to practice are physicians with
valid licenses.
3b. No migrants
denied asylum are persecuted migrants.
3c. Some politicians who want to increase taxes are politicians
who defend Social Security.
3d. Some proponents of civil unions are
not proponents of gay marriage.
Change the instructions in 4.4: III to “Determine whether the
following immediate inferences are valid or invalid from the Boolean
standpoint,” and do exercises 4.4 III: 1-20.
25 Oct.: Re-read section 4.7. Do
exercises 4.7: I: 1-30, including those exercises marked with a star. Use the
same capital letters you used earlier (to express predicates) now to express
terms, as given in this homework
help.
27 Oct.: Do exercises 4.7: I: 31-60,
including those exercises marked with a star. Use the same capital letters you
used earlier (to express predicates) now to express terms, as given in
this homework help.
V. Categorical syllogisms:
30 Oct.: Read enough of pp. 237-238 in Section
5.1 to understand the concepts of syllogism, categorical
syllogism, and the first three conditions of standard
form (our use of Venn diagrams allows us to ignore the fourth
condition). Read section 5.2, but only from the beginning to
the top of p. 251 (since we’ll be using just the
Boolean – not the Aristotelian – interpretation of categorical propositions).
Change the instructions in 5.1: I, 5.1: II, and 5.2: I to just “Use
Venn diagrams to determine whether the following standard-form categorical
syllogisms are valid or invalid from the Boolean standpoint,”
and do exercises 5.1: I: 1-5 and II: 1-10; and 5.2: I: 1-20.
1 Nov.: Do exercises 5.2: II: 1-10. Note that
the instructions are misleading, since there’s no such
thing as “the” (one and only) conclusion that is validly implied by a pair of
propositions. So if the two propositions taken together imply a conclusion that’s not logically equivalent to either
of the premises, then write this down in standard form. (For example, don’t write down “No M are P”
as a conclusion that follows from a premise of the form “No P are M,”
even though this inference is of course valid.) If the premises don’t entail any such conclusion, then write “no
conclusion.” Fortunately, the use of Venn diagrams renders the whole
discussion in 5.3 unnecessary, so you don’t have to
read it. Instead, change the instructions in 5.3: II to just “Use
Venn diagrams to determine whether the following categorical syllogisms are
valid or invalid from the Boolean standpoint,” and do
exercises 5.3: II: 1-10. Also read section
5.4. Ignore the phrase “or the rules for syllogisms” in the second
sentence in the instructions for exercises 5.4, and do exercises 5.4: 1-10.
3 Nov.: Read section 5.5. Ignore the phrase
“or the rules for syllogisms” in the first sentence in the instructions for
exercises 5.5, and do 5.5: 1-15. Also, change the instructions in 1.5:
I and 1.5: II to “Use Venn diagrams
to show why the following standard-form categorical syllogisms are invalid from
the Boolean standpoint,” and do 1.5:
I: 1-10 (including those exercises marked with a star), and 1.5:
II: 5, 6, 8 (these three exercises are a little tricky).
6 Nov.: Catch-up day.
VI. Enthymemes
8 Nov.: Read section 5.6. Do exercises 5.6:
I: 1-15 along with 5.6: II: 1-15. To do these, first complete the
Venn diagrams for either the two premises or one premise and the
conclusion. Then do your best to supply either (1) the conclusion or
(2) the other premise. If it turns out that
there’s no way to fill in such that the argument is valid, then indicate what
would be the best guess at (1) or (2). If there’s no way to supply (1) or (2) that would render the
argument valid, then state that the enthymeme is invalid.
10 Nov.: Do exercises 5.6: III:
1-10.
13 Nov.: Change the instructions in 2.1
to “Treat the following arguments as enthymemes. Determine whether the missing
statement is a premise or a conclusion. Then supply the missing statement,
attempting whenever possible to convert the enthymeme into a valid argument.”
Do exercises 2.1 II: 1-10, including those exercises
marked with a star.
VII. Informal logic:
Please note: for all of the
assignments for the rest of the semester, please also do the exercises marked
with stars.
Wednesday, November 29: Read
section 1.3 and this handout (again, especially the parts
on inductive logic). Do exercises 1.3: I: 1-30 and III:
1-15.
Friday, December 1: Read
section 1.4. Do exercises 1.4: I: 1-15, II: 1-15, III: 1-20, and V: 1-15.
Monday, December 4: Read
3.1 (“Fallacies in General”) and 3.5 (pp. 167-172) to solidify the basic
idea of an informal fallacy, but don’t worry about the
fact that most of the fallacies mentioned there will be covered in future
reading assignments. Do exercises 3.1: 1-10. If an
argument commits a formal fallacy that has a name, give its
name (see 6.6: pp. 323, 326-327, and 329-330), which will be either “affirming
the consequent” or “denying the antecedent.”
The following chart may help keep things a bit clear:
Arguments:
bad: good:
formal invalid
deductive valid
deductive
Logic:
informal fallacious
inductive or deductive sound
deductive or cogent inductive
Also read, in 3.2, section 4
(“Argument Against the Person [Argumentum
ad Hominem]”: pp. 116-119, including the Tu quoque variety); and, in 3.3 (“Fallacies of Weak
Induction”) sections 9 (“Appeal to Unqualified Authority”: pp. 128-129) and 10
(“Appeal to Ignorance”: pp. 130-131). These fallacies apply only
to inductive (not deductive) arguments. Much
of this material and the material dealt with in subsequent assignments is summed up in this handout, which is a condensed version of this handout, which is probably unnecessarily complicated.
Do the following exercises:
3.2: I: 2, 6, 10, 11, 16, 17, 18, 23, 24;
3.3: I: 3, 7, 9, 10, 11, 14;
3.3: III: 3, 4, 6, 12, 14, 17, 20, 22, 23, 27, 29;
3.4: III: 1, 9, 16, 17, 32, 36, 45; and
3.5: I: 6, 10, 14, 18, 24, 32, 40, 43, 44, 49, 51, 52, 53, 56.
In these exercises, whenever possible treat the argument
as an enthymeme, and state the missing but assumed premise
that would render the argument valid. Note that, in general, the argument
is weak if this missing assumption is false (and, in
general, strong if this missing assumption is true).
Wednesday, December 6: Read
the rest of 3.3 (“Fallacies of Weak Induction”), i.e., sections 11-14 (pp.
131-138); this covers the fallacies of Hasty Generalization, False Cause,
Slippery Slope, and Weak Analogy.
Do the following exercises:
3.3: I: 1, 2, 4, 5, 6, 9, 12, 13, 15;
3.3: III: 1, 7, 11, 15, 19, 27, 28, 30;
3.4: III: 8, 11, 13, 22, 33, 37, 38, 46, 48; and
3.5: I: 7, 9, 12, 13, 15, 18, 19, 20, 22, 25, 27, 29, 33, 36, 40,
41, 42, 43, 47, 48, 49, 52, 55, 57, 58, 60.
In these exercises, whenever possible treat the argument
as an enthymeme, and state the missing but assumed premise
that would render the argument valid. Note that, in general, the argument
is weak if this missing assumption is false (and, in
general, strong if this missing assumption is true). These
fallacies apply only to inductive (not deductive) arguments.
Also read, in 3.4, section 18 (“Suppressed Evidence:” pp.
150-151). Note that, in general, arguments that commit the fallacy of
Suppressed Evidence are inductive, weak, and
hence uncogent.
Do the following exercises:
3.4: I: 9, 16;
3.4: III: 30; and
3.5: I: 1, 13, 28, 30, 54, 59.
In these exercises, state what “evidence” is not
mentioned as a premise, but that, if true, would render the argument
weak. These fallacies apply only to inductive (not
deductive) arguments.
The remainder of the assignments
cover fallacies that apply to either inductive or deductive arguments:
Friday, December 8 (1st
assignment; worth one assignment): Read,
in 3.2, section 6 (“Straw Man”: 120-121); and, in 3.4, sections 16 (“Complex
Question”: pp. 148-149) and 17 (“False Dichotomy”: pp. 149-150). Many of these
arguments can be construed as valid,
where those that commit fallacies are valid but unsound;
i.e., the fallacies assume a false premise, whether explicitly or implicitly.
Do the following exercises:
3.2: I: 8, 19;
3.3: III 10;
3.4: I: 1, 5, 11, 17, 18, 22;
3.4: III: 15, 20, 25, 44, 50; and
3.5: I: 3, 11, 17, 20, 37, 45.
If any of these arguments commits a fallacy (and most, but not
all, of them do), explain why it does. That is, state (6) how
the argument mischaracterizes what someone else has said; (17) what the two
statements of a complex question are, and why one of these statements might be false;
or (17) what disjunction is assumed and why it might be false, i.e., why there
might be more than just the two alternatives mentioned in the disjunction.
Friday, December 8 (2nd
assignment; worth one assignment): Read,
in 3.2, section 8 (“Red Herring”: pp. 122-123); and, in 3.4, sections 15
(“Begging the Question” [Petitio Principii]: pp. 145-147), 19 (“Equivocation”: pp.
152-153), and 20 (“Amphiboly”: pp. 153-154). Unlike the exercises in the
previous assignment, the arguments in this assignment that commit fallacies
generally don’t do so because they assume some false
premise. Arguments that commit the fallacies of Red Herring or Begging the
Question may well be sound (or cogent), but are fallacious because they still
fail to meet the pragmatic goal of arguments: giving someone a good reason to
believe something that the person doesn’t already believe. A Red Herring is an
argument that isn’t on the same topic as one’s
opponent’s argument; and an argument “begs the question” if it assumes a
premise – whether explicitly or implicitly – that’s at least as controversial
as the conclusion. Equivocations and amphibolies are arguments that are really
invalid (or weak), but might appear valid (or strong) because of a wrong
interpretation of the meaning of at least one statement in the argument.
Equivocations are based on interpreting two (or more) occurrences of the
same word as having the same meaning, whereas in fact they
have different meanings; amphibolies are based in misinterpreting the meaning
of a statement that’s ambiguous because of its grammar.
Do the following exercises:
3.2: I: 3, 13, 21;
3.3: III: 13, 24;
3.4: I: 3, 4, 7, 8, 10, 15, 20, 23, 24, 25;
3.4: III: 2, 4, 7, 14, 23, 26, 27, 31, 34, 35, 39, 40, 42; and
3.5: I: 1, 3, 5, 9, 13, 16, 20, 23, 26, 28, 28, 30, 31, 32, 38,
39, 41, 42, 46, 51, 52, 53, 54, 56, 59.
If any of these arguments commits a fallacy (and most, but not
all, of them do), explain why it does. That
is, state (8) why the argument given isn’t relevant to the opponent’s argument;
(15) what premise – whether explicit or implicit – that’s no less controversial
than the conclusion is “begged.” or assumed; (19) which word is interpreted
equivocally (i.e., with different meanings in different occurrences) so as to
render the argument weak or invalid; or (20) which statement in an amphiboly is
misinterpreted and what the statement really means.
Monday, December 11, 1:00-2:50 p.m., in our regular
classroom: Make-up’s; you may make up any four quizzes of your choice, whether or
not you took them originally took them. For every quiz you missed due to an
excused absence that we’ve discussed, you may take an
additional make-up quiz. This period
will begin with our final, 12th,
quiz; it will cover the informal fallacies we’ve
studied. Jake and I will grade these quizzes as quickly as possible as you
hand them in, so that you can decide whether you’d
like to count this quiz as one of the ones you’d like to make up.