One of the most important things you learn as a result of training in rational reconstruction is the distinction between what someone says and what someone is.  The inability to separate a reasoner from her reasoning is responsible for a lot of uncharitable interpretation, as well as a lot of misguided criticism.  For example, whenever we suspect a person of saying something hypocritical, we naturally focus attention on his character.

• Marcus:  I notice you're putting on quite a bit of weight lately, Missy. That's not healthy. You should eat less junk food food and try getting a little more exercise.
• Melissa: How dare you say that to me when when you sit around on your ass all day eating chicken nuggets and playing video games!  Get some exercise yourself, slug.

Melissa's reaction is perfectly human, but it really doesn't have anything to do with what Marcus said.  In other words, even if if Marcus really has no right to say this sort of thing to Melissa, that fact itself has no bearing on whether Marcus has given Melissa some good advice and good reasoning in support of it.  Most of us don't deal particularly well with personal criticism, especially when it is coming from people who irritate us.  Professional athletes typically think they've got nothing to learn from people who have never played the game at their level.  Soldiers think people who have never been to war have no business trying to run one. Poor people are offended when others who were born into wealth tell them they have to save their money.  Again, all perfectly understandable reactions, but all equally problematic from a logical point of view. 

"Ad hominem" is Latin for "against the person".  In logic, ad hominem reasoning is any attempt to discredit a conclusion by focusing attention on the motives, character, or individual circumstances of the person offering the reasoning rather than examining the reasoning itself.  People usually speak of ad hominem arguments, but ad hominems often take the form of explanations. Specifically, ad hominem reasoning, often attempts to refute the reasoning that is given for some conclusion by explaining why the person making the argument actually holds that view. 

We define ad hominem reasoning as follows:

Ad Hominem

Definition:  Evaluating  reasoning by calling attention to the character, actions or personal circumstances of the reasoner, rather than examining the reasoning itself.
MOI:  Show how the the example focuses attention on the character, actions, or personal circumstances of the reasoner rather than examining the reasoning itself.

Example 1

Of course dentists say that everyone should have a teeth cleaning twice a year to prevent cavities and gum disease.  Why wouldn't they say that?  That's how they make most of their money. They'd recommend having one every day if they could get away with it.

Analysis

In this example it is claimed that the reason that dentists recommend that people get their teeth cleaned twice a year is to make more money.  Even if this is true, it ignores the argument that it helps to prevent cavities and gum disease.

Example 2

Maureen:  Joe said that stopping to help that gal with her flat tire was the right thing to do because it was getting dark in a nasty neighborhood and who knows what sort of seedy characters might have stopped and taken advantage of her before a tow truck arrived.  But, Doris, I just can't help but notice that the first time Joe Bob ever stops anywhere to help anyone with anything is for a chick who looks like she's on her way to a photo shoot for Penthouse. 

Analysis

Maureen ignores Joe's reason for stopping to help the stranded motorist by suggesting that he only did it because the motorist was an attractive young lady.

Example 3

The tobacco company Philip Morris defends it's right to sell  a product that kills hundreds of thousand of Americans a year and millions more people worldwide by claiming that they are only supplying a product that millions of people want. It also claims to spend millions of dollars annually educating kids about the dangers of smoking.  But Philip Morris does not simply supply the product, they promote it.  And they know that when kids see ads by a cigarette company telling them not to buy their product, that just makes them want it even more.  By playing the role of a "company that cares" Philip Morris is effectively softening public opposition to their deadly product.

Analysis

This example ignores Philip Morris' argument that it has a right to sell cigarettes by attacking it's campaign to discouraging underage smoking as insincere.

Example 4

Chub:  I don't care what Alice says about the Atkins diet helping helping her drop 40 lbs in 3 months. The bottom line for me is that she likes the diet because it lets her eat junk food, and that's just wrong. She just doesn't have the discipline to stop eating stuff that is bad for her.

Analysis

Here Chub ignores Alice's reasoning in favor of using the Atkins diet by explaining why Alice likes the Atkins' diet in terms of Alice's attraction to junk food.

Example 5

Howard:  Maggie, I don't get it.  How can you, a lifelong carnivore, an accomplished griller of flesh, see one documentary about livestock and poultry farming and suddenly decide to become a vegetarian?  Cruelty, schmuelty, I say.  Do you have any idea how Totally Un Fun it is going to be to eat with you from now on?  Think of our marriage!

Analysis

Here Howard ignores Maggie's reasons for becoming a vegetarian and focuses on her personal circumstances instead, namely that she will suffer for becoming a vegetarian.

Example 6

Quinton:   You know, when I was younger I used to think people would conserve energy because it's the right thing to do.  I just don't believe that anymore.  I know all these really nice, high-minded people talking about how they're so into recycling and buying organic baby foods, and how bad it is that we're killing people in Iraq to get their oil, but then I see them driving to their yoga classes in their friggin' SUV's. People are just so full of crap, you know?  You want to breathe clean air again? Cut traffic in half? Get people to stop driving trucks? Make us less dependent on foreign oil so we don't have to kill people to get it? All we have to do is crank the price of gas up to 10 dollars a gallon.  I'm all for it.

 

Cleo: You are nuts, man. How can you even think that when you commute 60 miles to work?  What are you, some kind of masochist?

Analysis 

Here Cleo ignores Quinton's argument that high gas prices will do a lot of good in the world, by focusing attention on Quinton's personal circumstances, namely that high gas prices will make his own life more difficult.

Here is a final example in which both Staw Man and ad Hominem are committed.

Example 7

Jesus Christ, I am just sick of that Reverend Tom Baxter preaching to us about love.  Love thy neighbor! Love thy enemies!  Love thy neighborhood child molester!  After that affair he had with Wilma Barrington last year you'd think he might realize that lovin' your neighbor's wife just ain't a particularly bright idea.

Analysis 1

This example commits a straw man by mischaracterizing the reverend's exhortation to love ones fellow man in a weakened form.  The preacher is not counseling romantic love between neighbors, but forgiveness and good will.

Analysis 2

This example commits an ad hominem against the reverend by ignoring his advice and focusing attention on the fact that, given his past conduct, continuing to give this advice makes the reverend the subject of ridicule among his congregation.

Justified violations of the Principle of Charity

Although, the principle of charity forbids the use of ad hominem reasoning as defined above, it does not forbid the attempt to explain people's beliefs and actions as the result of prejudice, error, irrationality, stupidity, bad character, greed or whatever.  After all, these explanations are often correct.  The mistake of the ad hominem is that it ignores the reasoning provided for a conclusion and explains the conclusions causally instead. The habitual ad hominizer is someone who is unable to separate the reasoner from the reasoning, who can not understand that the truth of a statement, or the validity of a rationale has nothing to do with who has actually uttered it.

Example 8

• Billy:  Mom, did you know that the world used to be black and white?  That's why all those old pictures Uncle Eb look like that.  He told me.
• Mom: Billy, your Uncle Ebenezer is a liar.  He can't help it.  There's something wrong with him. Remember when he gave you cookies and glass of white paint for a snack?  I'm sure you do.  You were in the hospital for three days.

Mom's response matches the definition of ad hominem perfectly.  She is ignoring Ebenezer's reasoning and explaining his statement in terms of the fact that he is a liar.  But this seems perfectly justified.  Mom has basically had it up to here with Ebenezer's stories and feels she doesn't even have to hear the content of what he is saying to know that it should probably be ignored.  Of course, it's possible that Ebenezer is telling the truth this time, but so what? We can't be attentive to all possibilities and we are not logically required to try. In the end, what makes Mom's ad hominem permissible is that she actually has independent evidence that what Ebenezer says is false.