abstraction: the fourth pillar

I thought there were three pillars to OOO as suggested here. In Googling it some, it kinda seems like some lists include abstraction as a fourth pillar. In many ways this is a lot like encapsulation in that in both cases you are trying to expose what is important and marginally hide that which is merely necessary that should draw the eye less sort of like the distinction between the "Wizard" of Oz and the man behind the curtain. (We want to keep him behind a curtain.) However, that said, encapsulation is something in particular, very particular, and has to do with how gunk is kept in a class itself. Abstraction will have you pulling stuff out of a class to another class.

 
 

Addendum 2/22/2019: OOO stands for Out Of Office and really OOO here should be OOP for Object-oriented programming.