Parallels between Mike and Jesus Christ - one obvious interpretation of Mike\'s story is a post-modern 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, 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 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.
The Spiritual Importance of Sexuality - In his time on Earth, Mike slowly learns about his own race, and what characteristics define humankind. The narrator tells us early about the most important difference between human beings and Martians: 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 gifts 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 Mike discovers sex, the ultimate \"growing-closer.\" He believes that the mental bond shared between lovers during sex is the deepest \"grokking\" known.
Powerful Institutions and their tendency towards abusing their power - 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 being observed and cared for. In fact, he is a 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 this tendency is often abused to override basic morality. This is practised by the Fosterite church as it is by 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.