The theory states that, with a subconscious set of mental "filters" formed from their beliefs and experiences, every individual interprets this same world differently, hence "Truth is in the eye of the beholder".
This is not necessarily meant to imply that there is no objective truth; rather that our access to it is mediated through our senses, experience, conditioning, prior beliefs, and other non-objective factors. The individual world each person occupies is said to be their reality tunnel. The term can also apply to groups of people united by beliefs: we can speak of the fundamentalist Muslim reality tunnel or the scientific materialist reality tunnel.
A parallel can be seen in the psychological concept of confirmation bias - our tendency to notice and assign significance to observations that confirm our beliefs, while filtering out or rationalizing away observations that do not fit with our prior beliefs and expectations. This helps to explain why reality tunnels are usually transparent to their inhabitants. While it seems most people take their beliefs to correspond to the "one true objective reality," Robert Anton Wilson emphasizes that each person's reality tunnel is their own artistic creation, whether they realize it or not.
It is believed that through various techniques one can break down old reality tunnels and impose new reality tunnels by removing old filters and replacing them with new ones, new perspectives on reality - at will. This is achieved through various processes of deprogramming using neuro-linguistic programming, cybernetics, hypnosis, biofeedback devices, meditation, controlled use of hallucinogens, and forcibly acting out other reality tunnels. Thus, it is believed one's reality tunnel can be widened to take full advantage of human potential and experience reality on more positive levels. Robert Anton Wilson's Prometheus Rising is (among other things) a guidebook to the exploration of various reality tunnels.