O N E S E L F
Pretty much an self-reflecting concept: remember that when you point the finger at another human, four are pointing at yourself! We basically spend our entire lives on the 'ledge' between knowledge of self and knowledge of the world around us. I've always said: "We don't know everything, but we pretty much know how well we know it": "I don't know" is a sort of intuitive answer that does not require much thinking.
It is common sense to know as much about the outside world as you can. But as you learn, you will notice that it all boils down to a limited number of patterns that apply in many different places. Yes, the Grand Overall Design is holographic in nature: the patterns repeat on all levels, even in the concept we call language: how else could I come up with Acrosstic after Acrosstic, written down in the flow of the moment?