Thanks for this additional information caliptrix. 

DÝR and its variants are derivatives of the verb DEMEK "to say", which is DER in the 3rd person singular.

YOR, and its derivatives, as in the sense of GIDIYORUM, SEVIYORUM etc is also a derivateive of the verb YÜRÜMEK, which means to walk.

It is virtually impossible to recognize these forms in Modern Turkish simply because they have been lost.

I know this won´t make any sense to someone learning Turkish, but this is where they come from.

Actually -dir comes from durmak.

dir < tur-ur (aorist 3rd person of durmak. means "stands")

güzel-dir < güzel turur ("it stands beautiful"  and it bacame over time "it is beautiful")

 - if you can´t agree amongst yourselves - what hope is there for us?? 

 Well all these contrýbute to a certain logic or image of how the language came about. I mean like every one of these is way to remember it more easily.   Oops, truth be told, my glass is already half empty when I wrote this! Bizim için ne umudýr!

 That is really interesting. So, DIR dervided from DUR like YOR derived from YUR. I had always assumed that DIR must have had something to do with DER/DEMEK as in making a statement about something. DUR sounds more logical.