Often when I am writing, I'll come across plots that, even after I've ironed them out, they feel like they are half plots, like there is another plot that somehow fits into the structure, making a whole story. I outlined and wrote a few chapters of a piece called Starseed which dealt with a group of random humans accidentally taking an experimental drug which put them in direct contact with extraterrestrials, thereby resulting in them assembling into a group and hijacking a spacecraft to Sirius. But that ending felt very contrived, and it was more of a vehicle for conveying the memes of Timothy Leary than anything else. Another story was fully written out. I was calling it The Wanderer, and in its original form (for a high school class) it involved a physicist who, upon exposure to a peculiar form of radiation, finds himself able to travel through time. A few years after high school, stirrings of a resurrection of this story--with which I was rather dissatisfied--came alongside my own psychedelic initiation, and the story was to gain a political slant, criticizing the War on (some) Drugs. It took place in the mid-1980s, and in it, a pharmacologist invents a drug which caused one to have an out-of-body experience, and at higher doses, actually caused one to teleport or time travel. I only got a few chapters into that manifestation of this story.
This present incarnation arises from a number of frustrated days of job-hunting upon my move to Austin, Texas. I spent a great deal of those days on the bus, and a friend had loaned me Radio Free Albemuth by Phil Dick. Wow. Then I read VALIS in between scribbling down ideas which were occurring to me, having been mobilized by PKD's narrative, as this was (and still is) being written for me, assembled for me in my own head.