Date: May 7, 2013 6:25 PM
Author: fom
Subject: Re: Collinear

On 5/7/2013 2:48 AM, William Elliot wrote:
> Let C be a collection of n points with the property that
> any line L with two points of C on it, has a third point
> of C on it.
>
> How is it that C is collinear, ie all points of C are
> on a single line?
>



Is this true?

If I recall, there is something from
design theory called a Pasch configuration.


ABC
AEF
BDF
CDE


C
|
B
|
| D
|
A----E---F

Maybe I am not recalling correctly.

This is better:

http://mathworld.wolfram.com/PaschConfiguration.html