Valentine Michael Smith is born on Mars to Earthling parents who die almost immediately after his birth, and is raised by the Martian race. Thus, his experience is entirely unique. He is unlike any other Martian because of his human physiology, and unlike any other human beings because of his Martian ways of thought. Mental powers that human beings assume are impossible, such as telekinesis and mind reading, are second nature to him, and his philosophies are entirely Martian as well—for example, if a "water-brother" (a close companion) wished him to will his body to die, Mike would be delighted to comply. Earth customs such as jealousy, desire, and lying are utterly foreign to him, implying that these qualities which often seem inherent to the human condition are learned.
Although Mike would seem to be the novel's central character—he is the titular stranger in a strange land—his journey toward understanding his human roots occurs largely in the margins of the plot. Instead, Heinlein focuses on Mike's companions' reactions to his growth. Therefore, Mike's leaps in "grokking" humankind often seem to occur quite precipitously. Under Jubal's tutelage he learns about the structure of human society; from his murderous encounter with Digby he learns self-reliance; from his days in the carnival he learns the value of showmanship; and from his days in Las Vegas he learns the nature of desire. From watching monkeys at the zoo he has the final revelation that makes him fully human. He learns that comedy and tragedy are inextricably intertwined, and that people laugh to soothe the pain of the horrors they have created for themselves. Mike weaves all of his knowledge, Martian and Earthling, into the Church of All Worlds, his noble attempt to help humankind rise above suffering.