This page is keyboard accessible:
• Use Tab, Shift + Tab keys to traverse the main menu. To enter a sub-menu use the Right Arrow key. To leave a sub-menu use the Left Arrow or the Escape key.
• The Enter or the Space key opens the active menu item.
• To skip the menu and move to the main content, press Tab after the page loads to reveal a skip button.
• To get back to the top of the page anytime, press the Home key.
• For more information, click here: Accessibility   Close this tip.

Note: Full functionality of this web page requires JavaScript to be enabled in your browser.

A Simplified Explanation of Gödel’s proof - Part 7




Part 7: Another Numbering System

This is the point in Gödel’s proof where we need a new function that is similar to the Gödel numbering function. The Gödel numbering function is not a number relationship, since it refers to symbols of the formal language that aren’t numbers, such as the symbol for equals, the symbol for plus, and so on.


We might suppose that we say that we’re going to use the Gödel numbering function only for symbols of the formal language that actually are numbers. So, if we call the Gödel numbering function GN(x), we say that we can only substitute the x by symbols of the formal language that represent numbers.


However, that still doesn’t make GN(x) into a number relationship – because the actual definition of the Gödel numbering function still refers to symbols other than numbers. In order for his proof to work, Gödel needs a function that is similar to the GN(x) function, but which is a purely number relationship.


The idea is that this new function will only take number values for its free variable, and provided you’re only inputting numbers, and the function only results in number values, this new function can do exactly the same thing as the Gödel numbering function. Since this new function doesn’t refer to anything other than numbers, and variables for numbers, and is defined only in terms of numbers, then it is a number relationship.


We can call this new function anything we like, but I’m going to call it the Basic Numbering function, or BN for short, or BN(x), where x is its free variable. (Footnote: In Gödel’s original proof, Gödel calls this function Z(n) - it is his ‘relation’ 17.) That means that whenever we put in symbols that are the symbols for a number, this BN function gives us the correct Gödel number – so we can get a Gödel number for any number we want.


You might wonder what happens if we try to substitute the variable of BN(x) by a symbol that isn’t a number. The answer is simple – the definition of BN(x) does not include any reference to specific values that are not number values. So trying to substitute a non-number value wouldn’t make any sense. It would be like trying to use any foreign word in a language and expecting it to make sense. With this function BN(x), wherever it appears, it has to be the case that only numbers can be substituted for its free variable x.

section divider


section divider





Diverse opinions and criticisms are welcome, but messages that are frivolous, irrelevant or devoid of logical basis will be blocked. Difficulties in understanding the site content are usually best addressed by contacting me by e-mail. Note: you will be asked to provide an e-mail address - any address will do, it does not require verification. Your e-mail will only be used to notify you of replies to your comments - it will never be used for any other purpose and will not be displayed. If you cannot see any comments below, see Why isn’t the comment box loading?.

section divider

The Lighter Side


Paper on the diagonal proof

There is now a paper that deals with the matter of language and the diagonal proof, see On Considerations of Language in the Diagonal Proof.

section divider

Other recently added pages

The Myths of Platonism


Goodman’s Paradox


The Platonist Rod paradox


The Balls in the Urn Paradox


section divider

Lebesgue Measure

There is now a new page on a contradiction in Lebesgue measure theory.

section divider

Easy Footnotes

I found that making, adding or deleting footnotes in the traditional manner proved to be a major pain. So I developed a different system for footnotes which makes inserting or changing footnotes a doddle. You can check it out at Easy Footnotes for Web Pages (Accessibility friendly).

section divider

O’Connor’s “computer checked” proof

I have now added a new section to my paper on Russell O’Connor’s claim of a computer verified incompleteness proof. This shows that the flaw in the proof arises from a reliance on definitions that include unacceptable assumptions - assumptions that are not actually checked by the computer code. See also the new page Representability.

Previous Blog Posts

Moderate Platonism

Descartes’ Platonism

The duplicity of Mark Chu-Carroll

A John Searle Inanity

Man versus Machine

Fake News and Fake Mathematics

Ned Block’s Blockhead

Are we alone in the Universe?

Good Math, Bad Math?

Bishops Dancing with Pixies?

Artificial Intelligence

Cranks and Crackpots

The Chinese Room


For convenience, there are now two pages on this site with links to various material relating to Gödel and the Incompleteness Theorem


– a page with general links:

Gödel Links


– and a page relating specifically to the Gödel mind-machine debate:

Gödel, Minds, and Machines

Printer Friendly

All pages on this website are printer friendly, and will print the main content in a convenient format. Note that the margins are set by your browser print settings.

Note: for some browsers JavaScript must be enabled for this to operate correctly.


Comments on this site are welcome, please see the comment section.


Please note that this web site, like any other is a collection of various statements. Not all of this web site is intended to be factual. Some of it is personal opinion or interpretation.


If you prefer to ask me directly about the material on this site, please send me an e-mail with your query, and I will attempt to reply promptly.


Feedback about site design would also be appreciated so that I can improve the site.

Copyright © James R Meyer 2012 - 2018