# Is this venn diagram correct? (pic in thread)

**URL:** <https://boards.straightdope.com/t/is-this-venn-diagram-correct-pic-in-thread/656437>\
**Category:** Factual Questions\
**Created:** [April 22, 2013, 10:12pm UTC](https://boards.straightdope.com/t/is-this-venn-diagram-correct-pic-in-thread/656437 "2013-04-22T22:12:05Z")\
**Posts on this page:** 4\
**Page:** 2

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**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\
**Post date:** [April 23, 2013, 3:35pm UTC](https://boards.straightdope.com/t/is-this-venn-diagram-correct-pic-in-thread/656437/21 "2013-04-23T15:35:19Z")

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[Here]([http://wikisend.com/download/212536/known](http://wikisend.com/download/212536/known) unknown.PNG) is the revised one. (No x’s this time, we’ll just assume each region has at least one proposition in it.)

Assumptions used to construct it:

All statements are either true or false, never both.  
All unknowables are unknown.

(I think that was it.)

No problem on the “effort” you mentioned by the way–I teach this stuff every day.

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**Author:** ![TATG](https://avatars.discourse-cdn.com/v4/letter/t/50afbb/32.png) [@TATG](https://boards.straightdope.com/u/TATG)\
**Post date:** [April 23, 2013, 3:37pm UTC](https://boards.straightdope.com/t/is-this-venn-diagram-correct-pic-in-thread/656437/22 "2013-04-23T15:37:20Z")

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I am guessing it is meant to say something like “god exists is true and unknown and unknowable, or god exists is false and unknown and unknowable”. And this requires a diagram that can handle disjunctions. See [SEP](http://plato.stanford.edu/entries/diagrams/) for Peirce’s and Shin’s extensions to Venn diagrams, which can do so.

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**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\
**Post date:** [April 23, 2013, 3:39pm UTC](https://boards.straightdope.com/t/is-this-venn-diagram-correct-pic-in-thread/656437/23 "2013-04-23T15:39:00Z")

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Actually, I think the first image might be close, assuming that ‘true’ and ‘false’ only refer to the sections outside of the overlap, as they are labeled. The circles themselves are NOT labelled, which makes the diagram incomplete at least. I suppose that the circle covering ‘true’ and ‘unknown’ might be ‘Things that are not known to be false’ and vice versa for the other one.

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**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\
**Post date:** [April 23, 2013, 6:23pm UTC](https://boards.straightdope.com/t/is-this-venn-diagram-correct-pic-in-thread/656437/24 "2013-04-23T18:23:30Z")

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> [@chrisk](#):
>
> Actually, I think the first image might be close, assuming that ‘true’ and ‘false’ only refer to the sections outside of the overlap, as they are labeled. The circles themselves are NOT labelled, which makes the diagram incomplete at least. I suppose that the circle covering ‘true’ and ‘unknown’ might be ‘Things that are not known to be false’ and vice versa for the other one.

That’s it. The diagram is correct if the 1 circle is actually “Things that may be true”, and the 2 circle is “Things that may be false”.

In which case the blue most-of-a-circle is things known to be true, the magenta most-of-a-circle is things known to be false, the aqua is unknown and the brown is unknowable.

Of course, that leaves aside the question of whether “God exists” makes sense as a true-false preposition.

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