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Read each of the arguments below and decide if is a deductive or an
inductive argument. Do not be distracted by whether you believe the
argument hai a true conclusion, or not. Whether the conclusion is true, in
your mind, has no bearing on whether the argument uses induction or
deduction.
1. Every duck I have ever seen has all white feathers. Therefore, I am
convinced that all ducks are white.
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Discussion: This is an inductive argument because the only reason given
for the conclusion is that all of the ducks seen to date are white. Since not
all the ducks in the universe have been seen (and seen to be white), there
is some degree of uncertainty in the conclusion. Ask yourself; "is there
any chance at all that the conclusion does not follow from the premise?"
Is there any chanc e at allthat the next duck this person sees will not be
white, even if all of the ducks seen, so far, are white? Of course there is.
Any argument that is based on limited observation is inductive by its very
nature.
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2.
The psychologists at the university have taken a poll of our students and
found that more than half of the graduating seniors at our school are
more interested in getting a job with a high salary than they are of
getting a job which helps humanity. The study makes this claim with a
95
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certaintY.
Discussion. This in an inductive argument because the conclusion only
holds with a 95o/o certainty. There is a 5Yo chance that the conclusion is
wrong. In fact, all scientific tests have a statistical based conclusion and
are inductive bY their very nature.
ducks caffy a perfect copy of the w-56 gene on chromosome 6'
However, it is a fact that a perfect copy of the w-56 gene causes all
feathers on a duck to be white in color. Therefore, all ducks who catry
such a perfect copy of the w-56 gene are white'
3. All
Discussion: this is a deductive argument. There is no chance of a duck
being anything but white, given these premises. Notice that the
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conclusion is, as a matter of fact, false because you and I know that not
all ducks are white. However, the argument a valid deductive argument.
4. Jimmy dresses very well and is well groomed. He also has good grades in
all of his classes. He donates a lot of time at the Senior Center and they
all love him. He has experience in politics because of his work on the
Clinton campaign. For all of these reasons, I believe he is the ideal
candidate for Student Government Co-exec.
This is an inductive argument. The argument is a good one and very
persuasive, but it is inductive, nonetheless. The list of reasons (premises)
is long and impressive, but certainly leaves room for doubt. For example,
if we added the premise that Jimmy is suspected of being a serial killer,
would the certitude of the conclusion be affected? I think so!
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Often, adding a premise that does not contradict one of the existing
premises is a good test to help determine if an argument is deductive or
inductive. A deductive argument (if it is valid), will not be affected by
the addition of a new premise (that does not contradict one of the existing
premises) but an inductive argument can become less (or more)
persuasive by such an addition. In the above inductive argument, adding
a premise that Jimmy is a suspected of being a serial killer does not
contradict any of the existing premises, yet it makes a profbund
difference in the certainty of the outcome.
On the other hand, adding any premise at all (which does not contradict
one of the existing premises) in argument#3, will not change the
certainty of the conclusion. Try it yourself. Add a premise like "all ducks
float on water" or "all ducks are serial killers". See, it doesn't change the
conclusion at all.
5. Ladies and Gentlemen of the Jury. I ask you to find the defendant, H.E.
Didit, guilty as charged. His fingerprints were found on the money. The
bank teller identified him. His car matches the color, make and model of
the get-away car and he bought a new washing machine for his mother
the day after the band was robbed. There can be no doubt that he is the
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robber.
Discussion: You decide. Once you dec,.le on this argument, ask yourself:
"Do you think all trials are the same kind of argument?"
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