God is omniscient, that is, he is aware of, sees, and knows all things, because he is wisdom itself and light itself. Wisdom itself is aware of all things. Light itself sees all things.
We showed above [Section 37] that God is wisdom itself. He is light itself because he is the sun of the angelic heaven that enlightens the intellect of all, both angels and people. As our eye is illuminated by the light of the physical sun, so our intellect is illuminated by the light of the spiritual sun—not only illuminated, but also filled with intelligence (depending on how much we love receiving it), since spiritual light is essentially wisdom.
This is why it says in David that God dwells in inaccessible light [Psalms 104:2; see also 1 Timothy 6:16]; and why it says in the Book of Revelation that in the New Jerusalem they do not need lamps because the Lord God enlightens them [Revelation 21:23]; and why it says in John that the Word that was with God and was God is the light that enlightens everyone who comes into the world [John 1:1, 9]. The “Word” in this last reference means divine wisdom. This is why the more wisdom angels have, the brighter a light they are in; and why when “light” is mentioned in the Word it means wisdom.
God is aware of, sees, and knows everything down to the least detail that happens in keeping with the divine design because it is a universal design that encompasses the smallest individual designs. (Individual things taken collectively are called universal, just as particular instances are collectively called something common or general.)
The universal design with [all] its individual designs is a masterwork so well connected together into one thing that you cannot touch or affect one part without something of a sensation flowing back to the others. Every created thing in this world has something comparable to this quality of the divine design in the universe.
Comparisons with observable phenomena will shed light on this. Throughout a human being, there are connective membranes and individual parts. The membranes enclose the individual parts, creating such a thorough connection that they become part of each other. This is accomplished through a common membrane around every unit in the body. This membrane wraps around the individual parts inside so that they act in a unified way to do whatever function or service that unit provides.
For example, the membrane around each muscle extends between individual motor fibers and wraps them with itself. The membrane around the liver, the membrane around the pancreas, and the membrane around the spleen also extend into the smaller parts inside these organs. The membrane around the lungs, called the pleura, extends in a similar way into the individual parts inside the lungs, as the pericardium also extends into each and every part of the heart. Likewise the peritoneum in general goes through anastomoses [points of communication] to join with all the membranes around individual organs. The same is also true of the meninges, the membranes around the brain. Using projecting filaments, these membranes extend into all the glands below, and extend through the glands into fibers, and through the fibers into every single thing in the body. This is how the head uses the brains to control everything under its power.
The sole purpose in mentioning these examples is to show you observable phenomena, so that you may have some idea of how God is aware of, sees, and knows everything down to the least detail that happens in keeping with the divine design.
from True Christianity, Sections 59, 60