The
identity of a speaker or writer is irrelevant to the validity of
his or her argument. It simply does not matter who uttered an argument.
All that matters is whether the premises lead to the conclusion.
There are only two ways to criticize an argument: (1) One or more
of the premises is or are false, or (2) the premises do not lead
to the conclusion. This is elementary logic, but it eludes many
people.
You
may have heard people discuss, with disfavor, "ad hominem"
arguments. Ad hominem is Latin for "to the man." An ad
hominem argument tries to attack characteristics of a person which
are irrelevant to the issue. When you evaluate an argument with
reference to the speaker, you are making an ad hominem response.
Again, this is wrong; you must respond to the argument, not "to
the man."
People
believe that the identity of the speaker is important because they
think they must be watchful for bias or hypocrisy. This is incorrect,
in the context of evaluating arguments. It is true that bias can
cause people to be dishonest, and you should be concerned about
bias when you evaluate whether or not to believe a person's
reports of fact. However, this is still irrelevant to an argument,
because the premises are either true or untrue on their own merits.
If you decide not to believe a biased speaker, it essentially means
that you refuse to evaluate an argument that contains the questionable
statement as a premise. It is no criticism of the argument that
you are skeptical of the reliability of its premises. In order to
refute the argument, you need to prove that one of the premises
is false.
Hypocrisy
is even less relevant to arguments. For example:
Speaker
2's comment is not responsive to the remark of Speaker 1. Speaker
1 was making a statement about what is wrong, and Speaker 2 changed
the subject by talking about Speaker 1's behavior. It is the
same when someone presents you with an argument and you begin to
discuss his or her identity. You are no longer discussing the argument;
you have changed the subject.
Just
look at arguments based on their merits. If you don't trust
a source that is reporting as fact one of the premises, it is okay
to say that you don't think you can evaluate the argument until
you have verified one of the premises. What is not okay is this
sort of thing:
Speaker
A: Marijuana should be decriminalized because the criminal
law should only forbid citizens from committing acts which harm
persons or the property of others.
Speaker B: You're just saying that because you like
to smoke it so much.
What
is relevant to an evaluation of A's argument is whether or
not his single premise, about what the criminal law should forbid,
is true. Whether or not he likes to smoke the stuff doesn't
enter into it. Always ignore the identity of the source when you
evaluate an argument.
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