"Grokking" has multiple meanings in the Martian language, but over the course of its usage in the novel, it tends to represent an understanding between two people, or a person and an object, or a person and an idea, so deep as to be equivalent to a psychic bond. When Mike groks that grass is meant to be walked on, he is not understanding an abstract concept but rather communing with the grass and feeling what it feels. Grokking soon comes to be synonymous with Mike's notion of God: a cosmic understanding that runs through all things and people and unifies the universe.
Jubal is an aficionado of sculpture, and in Chapter XXX he takes Ben on a tour of his sculpture garden. He is particularly fond of two Rodin sculptures and a sculpture of Hans Christian Andersen's "Little Mermaid." Rodin's "La Belle Heaulmière" represents to Jubal the bittersweet tragedy of female aging, and perhaps his own conflicted feelings about his own aging. Rodin's "Caryatid Who Has Fallen under Her Stone" represents courage and victory in ostensible defeat—a direct parallel to Mike's sacrifice at the end of the novel. Finally, "The Little Mermaid" is a mermaid who chooses to live on land, and thus a "stranger in a strange land" who nobly endures the pain her decision has brought, just like Mike's choice to immerse himself in human society.
Heinlein never makes it entirely clear whether his portrayal of Heaven—a humorous combination of traditional halo-and-wings angelic imagery with the structure of a corporation, with God as a boss expecting results from his employee angels—is meant to be taken literally or metaphorically. Heinlein implies that, like any religious assertion, it needs to be able to be understood both literally and metaphorically. So although it may seem counterintuitive that men like Foster and Digby, both of whom have committed multiple and grave sins in their lives on Earth, would be allowed into Heaven. On the other hand, the narrative suggests that it is their continuing influence on Earth among the many passionate Fosterites, that makes them as angels watching over the Earth. As angels, they literally influence Earth occurrences, and as deceased leaders who teachings continue to affect history, they metaphorically wield influence. When Mike joins their company at novel's end, we know that his impact on Earth culture will be lasting.