"Reality, to me, is not so much something that you perceive, but something you make." - Philip K. Dick 
In 1978, Philip K. Dick discussed his two favorite topics, saying:
my two preoccupations in my writing are "What is reality?" and "What is the authentic human?" I'm sure you can see by now that I have not been able to answer the first question. 
In that essay, regarding how reality is perceived differently by different people, Dick discussed his first story, which considered how a dog views our reality – a view concerned about the garbagemen who repeatedly steal our perfectly good garbage:
Certainly, I decided, that dog sees the world quite differently than I do, or any humans do. And then I began to think, Maybe each human being lives in a unique world, a private world, a world different from those inhabited and experienced by all other humans. And that led me to wonder, If reality differs from person to person, can we speak of reality singular, or shouldn't we really be talking about plural realities? And if there are plural realities, are some more true (more real) than others? What about the world of a schizophrenic? Maybe, it's as real as our world. Maybe we cannot say that we are in touch with reality and he is not, but should instead say, His reality is so different from ours that he can't explain his to us, and we can't explain ours to him. The problem, then, is that if subjective worlds are experienced too differently, there occurs a breakdown of communication... and there is the real illness. 
In his 1968 novel, Do Androids Dream of Electric Sheep?, Dick also took up the question of "What is reality?" Here, androids can be implanted with false memories, and since your memories dictate your world-view, they dictate your perception of reality. Thus, altering their memories of reality effectively alters their reality. "Knowing" that you are human is of no utility, since that could also be an implanted memory if you are actually an android. The definition of what constitutes reality is further blurred, in the novel, by the physical actions of Wilbur Mercer – a fictitious religious figure who, realistically, should not be able to affect reality, yet repeatedly does.
In his many writings, Philip K. Dick repeatedly addressed the question, but was never satisfied with the answers:
It was always my hope, in writing novels and stories which asked the question "What is reality?", to someday get an answer. This was the hope of most of my readers, too. Years passed. I wrote over thirty novels and over a hundred stories, and still I could not figure out what was real. One day a girl college student in Canada asked me to define reality for her, for a paper she was writing for her philosophy class. She wanted a one-sentence answer. I thought about it and finally said, "Reality is that which, when you stop believing in it, doesn't go away." That's all I could come up with. That was back in 1972. Since then I haven't been able to define reality any more lucidly. 
But then, neither has anyone else.
- ↑ Dick, Philip K. "The Android and the Human." 205. - The Shifting Realities of Philip K. Dick: Selected Literary and Philosophical Writings. New York: Random House. 1995. 183-210.
- ↑ 2.0 2.1 2.2 Dick, Philip K. "How to Build a Universe That Doesn't Fall Apart Two Days Later." I Hope I Shall Arrive Soon. Garden Dity, New York: Doubleday, 1985. 1-23. Print. Available: http://deoxy.org/pkd_how2build.htm