3 4 4C H A P T E R 1 7 ■ R e f u t a t i o nfrom something true to something that is obviously false, because, if everyone
stands up at a ball game, only the tallest people will be able to see bet-
ter. Kirsty’s response also shows why Matthew’s argument is invalid: Just
as one person’s ability to see can be affected by other people standing
up, because this raises the height that is necessary to see, so one person’s
ability to buy can be affected by other people having more money, if this
raises prices and thereby raises the amount of money that is necessary to
buy things.
This fallacy is often called a fallacy of composition, because it rests on the
mistaken assumption that what is true of the parts is also true of the whole
that is composed out of those parts. Each person in a class has a mother, but
the whole class does not have a mother. The earth might be heating up on
average in the long run even if some locations on earth have a cool summer
one year. These obvious mistakes can be cited to show that and why poten-
tially misleading arguments with the same form are no better. Lots of new
fallacies can be revealed in this way by deploying this method of refutation
by parallel reasoning.
Of course, not every refutation of this kind is so simple or so successful.
To understand the criteria that must be met for such a refutation to work, it
will be useful to consider a more complex example that reveals some of the
ways to respond to a charge of “That’s just like arguing... .” The example
concerns proposed legal restrictions on gun ownership. The National Rifle
Association (NRA) feared that these restrictions would lead to a total ban
on guns, which they opposed, so they widely distributed a bumper sticker
that read:
(1) If guns are outlawed, only outlaws will have guns.
The point, presumably, was that most people would add the suppressed
premise:
(2) It would be bad if only outlaws had guns,
and then reach the conclusion:
(3) Therefore, guns should not be outlawed.
This argument is not completely clear, partly because it is not clear who
counts as an “outlaw.” Some critics poke fun at this bumper sticker because
(1) seems true by definition if outlaws include anyone who breaks any law,
because anyone with a gun breaks a law if guns are outlawed. But what the
NRA probably means by “outlaws” are people who commit violent crimes,
such as robbery and murder. It is not strictly true that these will be the only
people with guns if guns are outlawed, since police and some present gun
owners would keep their guns. Nonetheless, these exceptions do not touch
the NRA’s main claim, which is that law-abiding people who would give up
their guns if guns were outlawed would then not have guns to defend them-
selves against violent criminals.97364_ch17_ptg01_333-350.indd 344 15/11/13 11:12 AM
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