The novel dealt with one Ed Firmley, a composer of scores for B-movie grade sci-fi films and a race of alien humanoids that had evolved without the development of sound as a basis of communication. The shamans of this alien race would on occasion have visions of Earth and its many sounds. Due to their unique evolution without sound the holy men were incapable of describing these experiences to the rest of their race. They just knew that the place they saw was their heaven. Meanwhile their race was modeled around sight and light, encompassing much more of the electromagnetic spectrum than the limited human vision. In fact, from their perspective, humans were capable of sight but nearly blind, such as a mole appears to a human. Their language involved the telepathic projection of color patterns in precise gradations and following mathematical formulas.
A spaceship carrying members of this race arrives on Earth and they mug Ed Firmley, a famous composer they quickly discover, as a cover-up for plugging a bio-chip into his head. This bio-chip is a digitized form of one of the aliens with a link back to the ship – essentially allowing everyone to experience Ed Firmley by proxy. The bio-chip is supposed to be passive, serving only as a means of relaying the mystic experience of sound to an entire race. Soon the alien presence in the bio-chip becomes bored of Firmley’s music, which is bland, schmaltzy schlock, and the pop music that he constantly listens to. As a consequence of this boredom, the bio-chip turns from being passive to active, controlling what Firmley listens to as well as feeding him mathematical formulas that he begins to use as the basis of his compositions. His career, from a financial perspective, dwindles, but he becomes a respected avant-garde artist. The active role the bio-chip takes in the relationship begins frying Firmley’s brain. At this point the aliens make themselves known and offer to remove the chip, but Firmley refuses. He sees himself as an artist whereas before, he was of no consequence, doing what he did simply for money. Firmley decides to give up his body to be transformed into a bio-chip which is in turn implanted into an alien brain. This will also lead to the eventual death of the alien host, but it offers Firmley a chance of experiencing their world of lights, our heaven.
However, Andrew M. Butler offers several alternative summaries which contradict the Lee/Dick interview cited above. A god-like being, Ditheon, fuses the Torah and Jesus Christ into a single being and takes over an individual. A scientist travels through the events of Dante's Divine Comedy, and a Beethoven-like composer is writing a film score, while pursued by aliens.
A scientist creates a theme park that is related to the events of his youth, whereupon a sentient artificial intelligence imprisons him within it, as a youth. He has to travel through Dantean realities (and artist, political activist and gay social networks in the Berkeley of the 1940s and 1950s) to return home and resume his life as an old man.
Alternatively, Dante's Divine Comedy is a portal to alternate subjective realities that represent three ways of perceiving the world.
"The owl in daylight" is a phrase Dick heard on television. It means "not to understand", or "to be blind".