Although the narrative of Stranger in a Strange Land operates on many different levels, one obvious interpretation of Mike's story would be as a postmodern retelling of the Jesus story. Before the novel even begins, we see that the title of Part One is "His Maculate Conception," a satirical reference to the mythology of Christ's immaculate conception. Although Mike's biological parents are entirely human, hence his conception being "maculate" rather than immaculate, Mike's birth and childhood on Mars make his origin as unique on Earth as Christ's. Like Christ, Mike begins to preach a message of peace and love to mankind, attracts followers. Mike's "ninth circle" is roughly equivalent to Christ's disciples, and he is persecuted by the Earthling institutions that seek to preserve their status quo at any cost. Mike is aware of his parallels to Jesus, so when he allows himself to be murdered at the end of the novel, he quite self-consciously engineers his death to reference Christ's, even positioning himself to be struck by the light in such a way that it appears he has an angelic halo.
As soon as Mike is discovered on Mars, he is subjected to the wills of massive Earth institutions. He is brought back to Earth and put in a hospital where he is ostensibly being observed and cared for. In fact, he is a de facto prisoner of Secretary General Douglas and his administration, who know that Mike's political importance, as a celebrity, a man of enormous wealth, and arguably the owner of planet Mars, is too great for them to allow him freedom. At one point Douglas considers murdering Mike to preserve his own political power. Any institution has a tendency toward self-preservation, but Heinlein demonstrates here that that tendency is often allowed to override basic morality. This is just as true of the Fosterite church as it is of the government, and the Fosterites of course are supposed to be, at their root, upholders of morality and goodness. And yet, though Jubal teaches Mike to mistrust institutions, Mike discovers that he needs to build an institution of his own, the Church of All Worlds, modeled largely on the Fosterites, in order to reach the public.
In his time on Earth, Mike slowly learns about his own race, and what characteristics define humankind. The narrator tells us early on that the single most important difference between human beings and Martians is that Martians lack bipolar (male/female) sexuality. By the end of the novel Mike has come to believe that sexuality, and the sexual act, are the greatest gift that belongs to humanity. Mike's first notion of intimacy, learned on Mars, is the act of "water-sharing" or drinking from the same glass as another. From there, Mike learns the human act of kissing, its own sort of water-sharing. Soon enough Mike discovers sex, the ultimate "growing-closer." He believes that the mental bond shared between lovers during sex is the deepest "grokking" known to man.