It is time for another one of my updates, and this time I bring you an important scientific discovery. I would like to bring to your attention a new logical fallacy, which I herewith name “argumentum ad urmomum”. It appears that noone else has ever thought of this name1, so I would like to claim it myself.


Argumentum ad urmomum (latin for “argument against your mom”) is a special case of ad hominem, in which a person attacks another person’s character instead of their argument.2 In argumentum ad urmomum, one person attacks another person’s mother in a desperate attempt to distract others from the actual argument. Allusions of sexual promiscuity, obesity or aspersions cast on the mental prowess of one’s mother are most common.3

Usage among adults

Argumentum ad urmomum is rarely used among adults unless as a last resort, mainly due to its limited efficiency. It used to be much more effective, but exactly because of this it has been used over and over again, rendering it, much like penicillin, useless. It appears to only be used in desperation, and usually signifies that the other person has won the argument. This is one of the few logical fallacies that actually works against the person invoking it.

Here is a short example that vividly illustrates the argument:
Prosecution: “The defendant was seen mortally wounding the victim by a stadium of a hundred thousand people. He was even on the big screen.”
Defense: “Your mom is fat.”
Prosecution: “The prosecution rests.”

In the above example, the evidence against the accused is so overwhelming, that the defense has to resort to argumentum ad urmomum in an attempt to misdirect the jury from the facts. Needless to say, the accused will probably be found guilty and sentenced to two consecutive life sentences in a maximum security prison in Nashville, Tennessee.4

Usage among adolescents

This argument is more frequently encountered in conversations between adolescents5 because they have not yet developed the skills necessary to present a clear, coherent argument (or, really, any argument at all). In this context, it oftentimes succeeds in its goal by causing the other party to retaliate with “no, your mom!”. An example:

Child #1: “<Generic female child’s name> was seen engaging public displays of affection with <generic male child’s name>. Also, various witnesses saw her in the playground with <generic male child’s name> when she had told you that she was going to stay at home. Therefore, I can only assume that she does not love you.”
Child #2: “You take that back! Your mom is fat!”
Child #1: “No, your mom is fat! You take that back!”

More often than not, a fight will erupt between the two parties.

Other uses

Other uses of argumentum ad urmomum include nonsensical responses, sarcastic retorts or allusions to sexuality (often involving double entendres). A few examples:

Person #1. “I am so hungry.”
Person #2. “Your mom is hungry.”

Person #1. “I hate your shirt.”
Person #2. “Oh yeah? Your mom!”

Person #1. “This screw is loose.”
Person #2. “So is your mom.”