3. IGNORE THE IDENTITY OF THE ARGUER

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 1: It is wrong to steal.

    Speaker 2: But you stole something yesterday!

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.