MENTAL MODEL · M2354

Last Thursdayism

Learn & MetacognitionHigh supportCognitive Science

Included

Version 1.0.0 · Updated 2026-07-30

CORE DEFINITION

A logically unfalsifiable theory: "The universe was created last Thursday, but with implanted memories of billions of years of history and fossil evidence." -

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

An extreme demonstration of unfalsifiability. - It is not just a joke; it is a reverse test of Occam's Razor (Rule 23). If a theory (such as certain conspiracy theories, deep state) can explain all evidence (including evidence against it), it is like Last Thursdayism—logically consistent but cognitively worthless. For those "perfect theories" that cannot be falsified, directly counter them with Last Thursdayism.

anchor

Anchor fast decisions

Based on the criterion of falsifiability (Popper): a theory has scientific/cognitive value only if it can be contradicted by any conceivable evidence. "Last Thursdayism" assumes that "all counter-evidence has been pre-planted," making it impossible for any evidence to refute it—it is thus logically consistent but completely lacking in discriminatory power. It reveals: a theory that can explain everything explains nothing. It is used to test whether other "perfect theories" are equally empty.

MINIMUM ACTION

In progress 0/4

Practice this model in one real situation:

Encounter a "perfect theory": a claim that can explain all evidence, including evidence against it.
Apply the test: ask "What evidence could refute it?" If the answer is "none/it's all planted," trigger Last Thursdayism.
Verdict: the theory is unfalsifiable and has zero cognitive value.
Counter: point out its emptiness by saying "This is like saying the universe was created last Thursday."

Check to track your progress (stored locally)

Learning progress0%

account_treeGenealogyexpand_more

menu_bookReferencesexpand_more

Source support: Explicit

link
en.wikipedia.orghttps://en.wikipedia.org/wiki/Omphalos_hypothesisZH · Explicit
verified