How does the author use illusion versus reality in Updike's, Toward the End of Time?

Updike uses illusion when Ben describes the large object that hangs in the sky as a second moon. No one knows for sure what it is, and when it fades into the atmosphere, Ben suggests that the object may, in fact, be the result of mass illusion. Ben also speculates that the beings in the spacecraft may have advanced intelligence. In order for them to appear in the skies in such a large ship, Ben believes, they must have mastered mind over matter. If they have done so, then perhaps all reality is an illusion.