# Gödel's Incompleteness Theorems

## Theorem

### Gödel's First Incompleteness Theorem

Let $T$ be the set of theorems of some recursive set of sentences in the language of arithmetic such that $T$ contains minimal arithmetic.

$T$ cannot be both consistent and complete.

### Gödel's Second Incompleteness Theorem

Let $T$ be the set of theorems of some recursive set of sentences in the language of arithmetic such that $T$ contains minimal arithmetic.

Let $\map {\mathrm {Cons} } T$ be the propositional function which states that $T$ is consistent.

Then it is not possible to prove $\map {\mathrm {Cons} } T$ by means of formal statements within $T$ itself.

## Also see

## Source of Name

This entry was named for Kurt Friedrich Gödel.

## Historical Note

**Gödel's Incompleteness Theorems** answered the second of Hilbert's $23$ (then) unsolved problems of mathematics.

Hence it ended attempts, like those of Alfred North Whitehead and Bertrand Russell, to develop the whole of mathematics from a finite set of logical axioms.

It also damages the idea of finding a finite set of basic axioms of physics to define all natural phenomena.

## Sources

- 1998: David Nelson:
*The Penguin Dictionary of Mathematics*(2nd ed.) ... (previous) ... (next):**incompleteness theorems** - 2008: David Nelson:
*The Penguin Dictionary of Mathematics*(4th ed.) ... (previous) ... (next):**incompleteness theorems** - 2014: Christopher Clapham and James Nicholson:
*The Concise Oxford Dictionary of Mathematics*(5th ed.) ... (previous) ... (next):**Gödel's Incompleteness Theorems**