What it is
Taking the lack of disproof as proof, or the lack of proof as disproof.
In the wild
No one has disproven it, so it is true.
How to answer it
Point out that not knowing is a third option, alongside true and false.
Burden and ignorance
Appeal to ignorance
Also called Argumentum ad ignorantiam
In depth
Origin and naming
From the Latin 'argumentum ad ignorantiam', 'argument to ignorance', where 'ignorance' means a lack of contrary evidence rather than stupidity. The term was likely coined by John Locke in the late 17th century. It thrives wherever the record is silent: McCarthyism treated an empty file as proof of guilt.
More places it shows up
Management has never proven the new tracking software is secure, so let's assume it's fine.
There's no evidence that this supplement causes harm, which makes it safe to take daily.
My uncle smoked for forty years and no doctor ever proved cigarettes caused his cough, so the link is invented.
Nobody on the team has shown our release schedule is unrealistic, so it stays as is.
How to spot it
- Notice when silence or a missing record is presented as positive evidence.
- Notice when 'you can't prove otherwise' is doing the work of 'here is my proof'.
- Notice when the argument ends exactly where the evidence should begin.