PERCEPTION

"Perception is reality."

It is a common phrase.

Perception is the the ability to see, hear, or become aware of something through the senses: the normal limits to human perception. It is the state of being or process of becoming aware of something in such a way, such as the perception of pain. It is  a way of regarding, understanding, or interpreting something through a mental impressions It also means having intuitive understanding and insight.
In science, it is the neurophysiological processes, including memory, by which an organism becomes aware of and interprets external stimuli.

The word itself comes from Old Middle English for  "seize, understand."

Reality is the world or the state of things as they actually exist, as opposed to an idealistic or notional idea of them. It is a thing that is actually experienced or seen, esp. when this is grim or problematic. Reality is a thing that exists in fact, having previously only existed in one's mind such as the paperless office may yet become a reality. It can also mean the quality of being lifelike or resembling an original. It is also the state or quality of having existence or substance such as death has no reality to young people.

In Philosophy, reality is an existence that is absolute, self-sufficient, or objective, and not subject to human decisions or conventions.


So, how a person sees, hears, or becomes aware of the world around him is his reality.

This is the foundation for the LOST mythology. Viewers has to use their own perception of the images and events on the screen to filter through their own experience and understanding to interpret the show for personal meaning and insight. This is why it is difficult to change a LOST viewer's mind on how they reacted or felt about the show. In a show about light and dark, there were no black and white answers.

Whether the island was actually a Pacific Island, or vegetation atop of alien tortoise, or a space ship, or a time vortex, or another dimension, it cannot set in stone.

Whether the characters were actually who they said they were is also open to debate. Were the characters "real" lives in the sideways world, and they dreamed of island adventures, or was it the other way around? Was Sawyer always a police officer who dreamed of being the bad guy? Was Hurley always a lottery millionaire or was he just a chicken fry cook who dreamed of being a millionaire?

LOST writers did not set down a set of story principles as authority;  incontrovertibly truths. As a result, we are left with any perception as reality.