Aiming for a more equal (more just) society.  

Yup.  That's it.

Some more info, should you want more than just my say so on that...

And you can find lots more from 

• Wikipedia
• New York Times
• Boston Globe
• various other bloggers.

Headquarters for the authors and the movement is at "The Equality Trust"

And yes, there are naysayers.  Read em all!  I can tell you which side I find more common sense and more believable.