Dick describes what sounds like a bipolar illness where he bounces back and forth between mania when he thinks he has figured things out and depression when he has lost his belief.
He has been engaged in scientific research the last seven years trying to figure out what the perturbation in the reality field was in 3-74, but the whole time he’s been afraid he is insane, especially with regard to hearing the AI voice.
He has a dream about someone who lived in a void and whose mind created a world in order to keep him from going crazy. The more this person scrutinized the world the more real it appeared. The only thing letting him know the world wasn’t real was a preprogramed voice which failed to do its job due to the increasingly convincing nature of the false world.
Dick’s takeaway from the dream is that what he knows as Valis (and the binary computer) is actually his own mind creating this imprisoning world.
Now that he seems to know for sure what is going on and that he was right that the world presented to us is not the real world, he wonders what the “utility” of the delusion is. We can either see the phony world (understand it but not believe it is real) or see the world as it truly is and be unable to make sense of it. Both approaches look like mental dysfunctions to him. Is the false world a gift from God? God might be the only way out of the “solipsistic trap,” so does this whole thing lead to him? Dick is embracing belief. He can’t prove God exists (it may well be a hallucination), but he is choosing to believe that God exists beyond himself.