# Re: Tarsky's Proof of the undefinability of truth.

```I suspect that this impossibility is because math uses concept of a
model, while truth refers to the match of facts of the model with facts of
the reality . Or at least to facts of a metamodel outside of the model.
That is AFAIK the Tarsky idea.```
```
For example,  "All men are mortal is true" .  Here suppose that "all men
are mortal" is a fact of a model  that admit inductive silogisms.

True in this case can express a match of the fact "All men are mortal" with
reality. or a  match with a metamodel in which the trueness of the model
"all men are mortal" is assumed as an axiom.

In both cases the whole statement "all men are mortal is true" is outside
of the model in which the statement "all men are mortal" is

However I can make an ordinaty mathematical model of matches between models
and metamodels. That is the boolean logic.

2013/3/23 Stephen P. King <stephe...@charter.net>

>  "In 1936 Tarski proved a fundamental theorem of logic: the *undefinability
> of truth*.   Roughly speaking, this says there's no consistent way to
> extend arithmetic so that it talks about 'truth' for statements about
> arithmetic.  Why not?  Because if we *could*, we could cook up a
> statement that says "I am not true."  This would lead to a contradiction,
> the Liar Paradox: if this sentence is true then it's not, and if it's not
> then it is.
>
> This is why the concept of 'truth' plays a limited role in most modern
> work on logic... surprising as that might seem to novices! ..."
>
>
>
>
> --
> Onward!
>
> Stephen
>
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--
Alberto.

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