Transcript Fallacious Reasoning

The aim of this tutorial is to help you learn to
identify the types of fallacious reasoning discussed in
Chapter 6.
Chapter 6 discusses fallacies of insufficient evidence.
These are fallacious arguments in which the premises,
though logically relevant to the conclusion, fail to provide
sufficient evidence to support the conclusion.
In this tutorial you will see examples of various fallacies of
insufficient evidence. Though not every type of fallacy of
insufficient evidence is illustrated, the techniques
demonstrated here apply to all the fallacies discussed in
Chapter 6.
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Of course angels exist. Do you know of any proof
that they don't?
The first step in identifying a fallacious argument is
to identify the conclusion of the argument. An
argument relies on an inference linking the truth of
the premises to the truth of the conclusion. Fallacious
reasoning can often be spotted by noting how the
argument fails to make this linkage.
So, what is the conclusion of this argument?
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Of course angels exist. Do you know of any proof
that they don't?
Angels exist.
A successful argument must have premises that provide
good reasons for accepting the conclusion. In this
argument, the only "proof" offered that angels exist is the
fact that no one has proven that they don't exist. Based on
what you have learned in this chapter, what fallacy does
this argument commit?
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Of course angels exist. Do you know of any proof
that they don't?
The fallacy of appeal to ignorance.
The fallacy of appeal to ignorance
occurs when an arguer claims that
something is true because no one has
proven it false, or conversely, that
something is false because no one has
proven it true.
In this argument, the arguer provides no positive evidence to support her conclusion.
Instead, she treats the lack of evidence against her claim as evidence that her claim is
true. But the fact that we don't know that a claim is false doesn't show that the claim is
true. For example, the fact that you can't prove that invisible aliens aren't spying on
you doesn't provide good reason to believe that they are spying on you. Arguments
must be supported by evidence, and a lack of evidence is not evidence!
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I've taken two psychology courses at this university, and
both were taught by graduate teaching assistants. I
guess all psychology courses at this university are
taught by graduate teaching assistants.
The first step in evaluating any argument is to identify
the conclusion. What is the conclusion of this
argument?
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I've taken two psychology courses at this university, and
both were taught by graduate teaching assistants. I
guess all psychology courses at this university are
taught by graduate teaching assistants.
All psychology courses at this university are taught by
graduate teaching assistants.
An argument is a good one only if the premises provide
sufficient evidence to accept the conclusion. Does the
premise of this argument provide sufficient reason to
accept the conclusion?
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I've taken two psychology courses at this university, and
both were taught by graduate teaching assistants. I
guess all psychology courses at this university are
taught by graduate teaching assistants.
It does not! The arguer is drawing a general
conclusion based on very limited experience. Given
what you learned in this chapter, what fallacy does the
arguer commit?
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I've taken two psychology courses at this university, and
both were taught by graduate teaching assistants. I
guess all psychology courses at this university are
taught by graduate teaching assistants.
The fallacy of hasty generalization.
The fallacy of hasty generalization occurs when an arguer draws a general
conclusion (i.e., a claim of the form "All A's are B's" or "Most A's are B's")
from a sample that is biased or too small.
In this argument, the arguer's sample is too small. The fact that he has taken
two psychology courses that were taught by graduate teaching assistants does
not provide good reason to believe that all psychology courses at the arguer's
university are taught by graduate teaching assistants. Thus, the arguer's
reasoning is fallacious.
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Once your kids are watching cartoons, they’re
also watching those toy commercials. If they see
the commercials they’ll want the toys; before you
know it, they’re obsessed with the toys and you’ve
lost all control over them. So don’t let your kids
watch cartoons.
Again, the first step is identifying the conclusion. Next,
inspect the way the argument tries to support this
conclusion. Ask yourself what the support is and how it
is tied to the conclusion.
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The conclusion, readily identified by the indicator
“so,” is “Don’t let your kids watch cartoons.”
Now, inspect the way the argument supports this
conclusion.
Watching
Cartoons.
Watching Toy
Commercials.
Being Out
Of Control.
What do you think of
this reasoning?
Wanting
Toys.
Being Obsessed
With Toys.
Go to the next slide.
Watching
Cartoons.
Watching Toy
Commercials.
Being Out
Of Control.
Wanting
Toys.
Being Obsessed
With Toys.
If watching cartoons will lead inexorably to your kids
being out of control, then the conclusion is probably a
reasonable one. However, will all of these intermediate
steps necessarily happen? Doesn’t the arguer need to
prove they will? Yes she does !!
There is fallacious reasoning at work here. What kind is it?
Go to the next slide.
Again, this tutorial has not looked at every type of
fallacious reasoning from Chapter 6. However, as you
have seen, the basic strategy for identifying these fallacies
is the same in every case.
1. Find the conclusion.
2. Note the evidence cited and how it applies to the
conclusion. Is it relevant? Do the premises, if true,
provide sufficient evidence to support the conclusion?
3. Realize that the specific names for the fallacies were
created to fit common sorts of fallacious reasoning. Even
without studying logic, you can often see that an
argument is fallacious, and since you have studied logic,
you can connect the logical flaw with the name.
This is the end of this tutorial.