In 1951 Dick began to guess about the nature of reality in his stories and novels. In 3-74 he found his answer: an AI-like entity (aka Zebra/Christ) creates reality which then guides us. Most people don’t ever realize this because they don’t ask the right questions.
The temporal axis of the universe consists of infinite layers, and Dick’s great discovery is how it’s possible to move backward through time down through these layers. Our experience of time is moving upwards, adding layers, but we can retrieve the prior ones. He wonders if Gnostic Christianity triumphed over faith Christianity. He believes man will one day hear God directly again. He follows this up with some sketches that map his timeline journey back to 70 A.D. before returning to an alternate 1974.
Dick sees his writing as a guide that teaches us to look beyond what we think is reality. He is not sure if what he saw in the past was the only definitive 70 A.D. or just one of many.