Checked fact 179818 Oct 2026Research

Theorem Proving in Lean 4 says: 'The sorry identifier magically produces a proof of anything, or provides an object of any data type at all.'

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The exact words it rests on

The sorry identifier magically produces a proof of anything, or provides an object of any data type at all. Of course, it is unsound as a proof method

What the source said when we opened it, on 18 Oct 2026.

The source

Theorem Proving in Lean 4: Propositions and Proofs
Lean FRO / Lean project

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Checked

Checked by the notis newsroom on 18 Oct 2026, against the source above.

In the story

How Lean checks an AI-written proof, and where that stops 18 Oct 2026

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In a sentence

“Theorem Proving in Lean 4 says: 'The sorry identifier magically produces a proof of anything, or provides an object of any data type at all.'.” ai notis, checked 18 Oct 2026. Source: Theorem Proving in Lean 4: Propositions and Proofs (Lean FRO / Lean project). https://ainotis.com/c/1798

As a reference (APA style)

ai notis. (2026, October 18). Theorem Proving in Lean 4 says: 'The sorry identifier magically produces a proof of anything, or provides an object of any data type at all.' [Checked claim 1798]. ai notis. https://ainotis.com/c/1798

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