RECognizing LogiCAL FALLACiEs 233You should use this drug because it has been clinically proven that it inhibits
the reuptake of serotonin and enhances the dopamine levels of the body’s
neurotransmitters.
The student’s argument may very well be true, but he hasn’t presented any
substantive evidence to demonstrate that the premises are true and that
the conclusion follows from the premises.- Confusing Cause and Effect. It is challenging to establish that one
factor causes another. For example, how can we know for certain that eco-
nomic class predicts, or is a factor in, academic achievement? How do we
know that a new president’s policies are the cause of a country’s economic
well-being? Authors often assume cause and effect when two factors are
simply associated with each other:
The current recession came right after the president was elected.
This fallacy states a fact, but it does not prove that the president’s election
caused the recession. - Appeal to Fear. One type of logical fallacy makes an appeal to read-
ers’ irrational fears and prejudices, preventing them from dealing squarely
with a given issue and often confusing cause and effect:
We should use whatever means possible to avoid further attack.
The reasoning here is something like this: “If we are soft on defense, we
will never end the threat of terrorism.” But we need to consider whether
there is indeed a threat, and, if so, whether the presence of a threat should
lead to action, and, if so, whether that action should include “whatever
means possible.” (Think of companies that sell alarm systems by pointing
to people’s vulnerability to harm and property damage.) - Fallacy of Division. A fallacy of division suggests that what is true
of the whole must also be true of its parts:
Conservatives have always voted against raising the minimum wage, against
stem cell research, and for defense spending. Therefore, we can assume that
conservative Senator Harrison will vote this way.
The author is urging readers to accept the premise without providing evi-
dence of how the senator has actually voted on the three issues. - Hasty Generalization. This fallacy is committed when a person
draws a conclusion about a group based on a sample that is too small to be
representative. Consider this statement:
Seventy-five percent of the seniors surveyed at the university study just
10 hours a week. We can conclude, then, that students at the university are
not studying enough.
What you need to know is how many students were actually surveyed.
Seventy-five percent may seem high, but not if the researcher surveyed just
400 of the 2,400 graduating seniors. This sample of students from a total
population of 9,600 students at the university is too small to draw the con-
clusion that students in general are not studying enough.
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