Realmatic Theory
Realmatic Theory refers to the structure of the Cosmere. There are three realms: Physical, Spiritual, and Cognitive.
“ I have come to see that each power has three aspects: a physical one, which can be seen in the creations made by Ruin and Preservation; a spiritual one in the unseen energy that permeates all of the world; and a cognitive one in the minds which controlled that energy. ”
“ All things exist in three Realms, Gaotona. Physical, Cognitive, Spiritual. The Physical is what we feel, what is before us. The Cognitive is how an object is viewed and how it views itself. The Spiritual Realm contains an object’s soul— its essence— as well as the ways it is connected to the things and people around it. ”
Physical Realm
Most of Brandon's published works take place almost exclusively in the Physical Realm. Of the three realms, it is the most readily understood, as it behaves in much the same way as our universe does.
Spiritual Realm
Extremely little is currently known about the Spiritual Realm. The few glimpses we have seen directly into the Spiritual realm involve all the Connections present in a given spot (relational, physical, and temporal) condensing such that the relevant things on both sides of those Connections are comprehended as though they were physically present.
However, it is believed by a few on Roshar that the Spiritual Realm is a place of absolute truth, where things exist in their pure forms.
Cognitive Realm
Very little is known about the Cognitive Realm. Brandon tends to be rather close-lipped on the subject.
During Interlude 8 in The Way of Kings, Geranid discovers that when she measures a flame spren and then notes down her findings that particular attribute of the spren ceases to change. In this instance it was the size of the spren that was affected. It is believed by a few that this is linked to something that happens within the cognitive realm.
On Roshar the Cognitive Realm is called Shadesmar.[3]
The setting for most of Mistborn: Secret History was the Cognitive Realm. Kelsier goes there after being killed by the Lord Ruler but finds a way to not "move on."