In this theory, I’ll often refer to the mind instead of the brain. The difference between the two is simple - a brain is a closed system of relationships that exist as a cluster of neurons (in the physical space); while a mind is an open system of relationships that exists between symbols (within the abstract space). A brain can die, while a mind cannot, and the function of the universe is to maintain a special mechanism of exchange between minds and brains.
Plato was an ancient Greek philosopher who lived between 429 BC and 347 BC. He was a mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Akademia in Athens.
Akademia was the first institution of higher learning in the Western world.
Plato along with his mentor Socrates, postulated a unique world-view called the Theory of Forms.
According to their Theory of Forms, our physical world is but a shadow of even greater shapes, called Universals, that reside in a hidden world of ideal forms. These distinct, yet immaterial substances inhabiting the World of Forms are responsible for reflecting our physical environment, which Plato called the World of Substance. According to their 'world-view', our world is essentially an illusion of a hidden world [of Forms].
In the 17th century, a philosopher named René Descartes brought Plato’s arguments further with his theory on Dualism. He claimed that the mind and brain were different entities inhabiting different realms in the universe. Descartes stated that 'the mind is distinct from the body and its substance is the essence of thought'.
To date, their theories haven't significantly gained traction within the physical sciences community.
Dualism is the fundamental concept that ties the abstract space to the physical space.