Believers in ESP claim to have the ability to obtain information without using the physical senses. Although this ability has never been proven by science; most people have experienced hunches, gut feelings, premonitions, intuition or other unexplainable ways of “just knowing” something. This only adds to the uncertainty of what is real.
After experiencing the world outside our minds with our limited and often inaccurate senses we then try to understand what is "real". This brings us into the realm of philosophy where the boundary between what is real and what is imaginary becomes even less definite.
In an effort to understand the experiences in our lives philosophers have come up with many theories. Instead of getting bogged down in the details I will use an oversimplification to make a point.
There is the belief called "dualism" which states that there are two distinct types of reality. The reality of mind which we all experience personally and the reality of matter which are altogether separate forms of existence; that consciousness is not physical and that matter is not conscious.
This is opposed to the belief that there is only one kind of existence. "Monists" are philosophers who believe that everything that exists falls into one and only one fundamental sort of substance. There are two main forms of monism. One is called "materialism". The other is called "idealism".
On the one hand materialism is the belief that everything is made of matter. There are no minds or souls or immaterial spirits. Physical matter is all that exists so that even the mind is only a physical phenomenon that can someday be completely explained by physical and chemical reactions.
On the other hand idealism is the belief that everything is of a mental nature; so that only mind and the objects of mind exist. Everything is composed of mental realities (e.g., thoughts, feelings, ideas, or will) with matter being only an illusion projected by the mind. Matter is seen as a sort of "virtual reality" with no such thing as actual solid physical matter, only ideas.
Some interesting quotes:
“Matter is derived from mind or consciousness, and not mind or consciousness from matter.”
-Tibetan Book of the Great Liberation
“God sleeps in the rock
Dreams in the plant,
Stirs in the animal
And awakens in man.”
“The aim isn't to degrade mind to matter, but to upgrade the properties of matter to account for mind, and to tell how from the dust and water of the earth, natural forces conjured a mental system capable of asking why it exists.”
-Nigel V. Calder