Actually, he doesn't need to know anything. When a person himself becomes Knowledge, he knows the Basis, the Principle, the Source of all knowledge. And everything else - detailing, concretization, orchestration of spaces and times.
The dichotomy itself disappears, there is no longer a clear line between knowledge and ignorance / ignorance. You know everything and always, only this knowledge is so open and accessible that we get scared of this and make ourselves comfortable in the shade of so-called abstract ignorance.
Everyone knows everything. There is not a single living being who is not omniscient. We are just ashamed of this knowledge. It's uncomfortable to know that you are mortal / immortal, what you did billions of years ago and what you will do billions of years in the future ... that there are no times and spaces, that there are only abstractions, that there is no reality / realities, that there is ...
What is there? Who is? Why is there? Why is there? As it is? You know the incredibly accurate answers to these terrible questions. Just slow down the implementation of these Answers, because only scraps can remain from our human shell with excessive acceleration ... Scraps from science and philosophy, from religion and tradition, from civilization and ethics with aesthetics ...
Everything. Enough. I won't. It seems that I've become too all-knowing :).
However, what about you? Are you not an omniscient person? Don't you know absolutely everything? And what is most interesting, at the same time you manage to remain an ordinary inhabitant of the Earth ... Do not show off in front of your neighbor, who may in fact turn out to be the Second Know-it-all. Don't you just tremble from the fact of your omniscience, eh?
However, you and I are saved by irony, the laughter of thoughts ... We are simply included in tautology. Thought is thought, feeling is feeling, man is man, porridge is porridge, ceiling is ceiling, matter is matter ... Word is word ...
We are we. I am me.
I am thought. I am knowledge. I am the feeling. I am ... We are ... You are ... Nothing like "you"? Martin Buber once famously spun this whirlwind "I and You", just a philosophical feast for the eyes.
But in fact there is no knowledge, even scanty, right? No, and that's it! As, however, and ignorance (as already suggested by dialecticians). There is something constantly mixed, a kind of third ... Edge, border ... Our understanding is the edge, understanding of the edge, boundaries.
How to go beyond your understanding? Become Understanding. Omniscient, all-flowing, steadily all-encompassing. And to know every atom of the Universe, and from this knowledge you want to jump, laugh or just be. As Castaneda wrote - are we just dust on the road? Such dust ...
Just be ignorant and become omniscient. But God, how difficult it is!
Oops, that would be live recursion. Can you imagine what the computing power would have to be to know how 2 pieces of quantum foam behaved in a billion million light years from Earth 43678 years and 4 seconds ago? So you still need to know what you need to know.