What it is
Declaring a claim absurd without giving any reason why.
In the wild
That is ridiculous, next question.
How to answer it
Ask directly which premise is false and why.
Attacks on the source
Ad lapidem
Also called Appeal to the stone
In depth
Origin and naming
From the Latin 'argumentum ad lapidem', 'argument to the stone'. The name commemorates Samuel Johnson's famous retort to George Berkeley's immaterialism: as Boswell records it, Johnson kicked a large stone and announced, 'I refute it thus.' Logicians took the kicking as the emblem of a dismissal that performs instead of argues.
More places it shows up
During the standup, the lead engineer glances at the prototype and says, 'This is nonsense,' then moves to the next agenda item without explaining what breaks.
A panelist on a news show hears the guest's housing proposal, laughs, and says, 'Nobody serious believes that,' and the host moves on.
At the family dinner, an uncle waves off his niece's career plan as 'childish' and asks someone to pass the bread.
In a group chat, someone replies to a linked study with a single laughing emoji, and the thread treats the matter as settled.
How to spot it
- Notice when 'ridiculous' arrives as a full stop rather than the start of an explanation.
- Notice when a groan, a laugh, or an emoji is asked to carry the entire weight of a refutation.
- Notice when you are left unable to say which part of the claim was rejected, because no part was named.