Chapter 30:
Fallacies of Presumption
Begging the Question
(pp. 349-351)
• Fallacies of presumption either assume
what is to be proved or incorrectly assume
that all the relevant information has been
given.
• All cases of begging the question are valid
deductive arguments, since every
statement entails itself.
Begging the Question
(pp. 349-351)
• Assuming the conclusion as a premise
– If you assume the conclusion you set out to
prove as a premise, often stated in different
words, the argument begs the question.
Since the premises are to provide reasons to
accept the conclusion, you’ve done so, but
there is no more reason to accept the
conclusion than there was to accept the
premises:
“I didn’t steal, since I didn’t take anything that
wasn’t mine.”
Begging the Question
(pp. 349-351)
• Arguing in a circle
– If there are several arguments and the
conclusion of the last is a premise of the first,
there is a circular argument:
Question: If you could live forever, would you
and why? Answer: "I would not live forever,
because we should not live forever, because if
we were supposed to live forever, then we
would live forever, but we cannot live forever,
which is why I would not live forever."
Begging the Question
(pp. 349-351)
• Question-begging epithets
– An epithet is an adjective, noun, or phrase
used to characterize a person or thing.
– If one characterizes a person or thing with an
epithet that corresponds to the issue at hand,
one has begged the question:
“All the evidence we have examined shows
that that liar Biggs is guilty of perjury.”
(Perjury is lying under oath.)
Complex Question (pp.351-352)
– Sometimes when we ask one question, we
assume that another question has been
answered.
– Asking a complex question as such does not
constitute an argument, and it is therefore not
a fallacy.
– Often the assumption is made that there is an
implicit argument, particularly when the
answer to the assumed question is
incriminating.
Complex Question (pp.351-352)
• It’s a fallacy only if it is part of an
argument.
– In this case, the complex question provides
the basis for an argument, as shown:
Instructor: When did you stop cheating in this
course?
Student: On January 29.
Instructor: Ah ha! So you admit you were
cheating in this course. I shall need to bring
this up before the Honor Council.
Complex Question (pp.351-352)
• Some complex questions do not provide the
basis for fallacious reasoning.
– You’re in court, and an attorney asks you, “Where
were you on the evening of June 27, 2003?” This
assumes that you were somewhere on the evening of
June 27, 2003, but if you’re old enough to understand
the question, you were somewhere on that evening.
– Many questions we are asked are complex. It is
reasonable to claim that there is a fallacy of complex
question, and therefore an implicit argument, only if
the question assumed to be answered is incriminating
or open. “When did David write the 23rd Psalm?”
assumes that the David of biblical fame wrote it,
which is an open question.
Suppressed Evidence
(pp. 352-363)
• When we develop an argument for a position,
we generally do not provide all the evidence on
both (or however many) sides of an issue.
• The fallacy of suppressed evidence is committed
when someone knowingly withholds relevant
evidence:
– Mr. Bigg, CEO of Bigg Enterprises, is presenting an
argument at a town meeting that the town should
allow him to build a new factory. He has stressed the
economic advantages to the community. If he failed
to mention in other communities where he has built
factories the crime rate rose markedly, air pollution
levels were seriously increased, etc., Mr. Bigg would
be guilty of the fallacy of suppressed evidence.
False Dichotomy (pp. 353-354)
• A false dichotomy is a disjunctive
syllogism with a false disjunctive premise:
Either Diana is a Socialist or a Communist.
She’s not a Socialist. So, she’s a Communist.
If Diana were a Republican, then the disjunctive
premise would be false, and the argument
would commit the fallacy of false dichotomy.