The Sally-Anne fallacy

Cross-posted from my blog

I’d like to coin a term. The Sally-Anne fal­lacy is the mis­take of as­sum­ing that somone be­lieves some­thing, sim­ply be­cause that thing is true.1

The name comes from the Sally-Anne test, used in de­vel­op­men­tal psy­chol­ogy to de­tect the­ory of mind. Some­one who lacks the­ory of mind will fail the Sally-Anne test, think­ing that Sally knows where the mar­ble is. The Sally-Anne fal­lacy is also a failure of the­ory of mind.

In in­ter­net ar­gu­ments, this will of­ten come up as part of a chain of rea­son­ing, such as: you think X; X im­plies Y; there­fore you think Y. Or: you sup­port X; X leads to Y; there­fore you sup­port Y.2

So for ex­am­ple, we have this com­plaint about the words “Afri­can di­alect” used in Age of Ultron. The ar­gu­ment goes: a di­alect is a vari­a­tion on a lan­guage, there­fore Marvel thinks “Afri­can” is a lan­guage.

You think “Afri­can” has di­alects; “has di­alects” im­plies “is a lan­guage”; there­fore you think “Afri­can” is a lan­guage.

Or maybe Marvel just doesn’t know what a “di­alect” is.

This is also a mis­take I was point­ing at in Fas­cists and Rakes. You think it’s okay to eat tic-tacs; tic-tacs are sen­tient; there­fore you think it’s okay to eat sen­tient things. Ver­sus: you think I should be for­bid­den from eat­ing tic-tacs; tic-tacs are non­sen­tient; there­fore you think I should be for­bid­den from eat­ing non­sen­tient things. No, in both cases the defen­dant is just wrong about whether tic-tacs are sen­tient.

Many poli­ti­cal con­flicts in­clude ar­gu­ments that look like this. You fight our cause; our cause is the cause of [good thing]; there­fore you op­pose [good thing]. Some­times peo­ple dis­agree about what’s good, but some­times they just dis­agree about how to get there, and think that a cause is harm­ful to its stated goals. Thus, liber­als and liber­tar­i­ans sym­met­ri­cally ac­cuse each other of not car­ing about the poor.3

If you want to con­vince some­one to change their mind, it’s im­por­tant to know what they’re wrong about. The Sally-Anne fal­lacy causes us to mis­tar­get our coun­ter­ar­gu­ments, and to mis­take po­ten­tial al­lies for in­evitable en­e­mies.

  1. From the out­side, this looks like “sim­ply be­cause you be­lieve that thing”.

  2. Another pos­si­ble mi­s­un­der­stand­ing here, is if you agree that X leads to Y and Y is bad, but still think X is worth it.

  3. Of course, some­times peo­ple will pre­tend not to be­lieve the ob­vi­ous truth so that they can fur­ther their das­tardly ends. But some­times they’re just wrong. And some­times they’ll be right, and the ob­vi­ous truth will be un­true.