a world without liars =

= a world without humans

= a world without strife
= a world without corruption 
= a world without pollution 
= a world with only truth 
= paradise

When trying to tell whether or not someone is lying...
"Also pay attention to what the person is saying, since people who are lying tend to give:

     - fewer facts and details 
     - less information about times and places"
http://sciencenetlinks.com/student-teacher-sheets/all-about-lying-honest/

Keep this in mind with politicians, the media, salesmen, etc. 
Basically, if their lips are moving, they're lying.