Valentine Michael Smith is a man who was raised by Martians. When Mike’s fellow humans return him to earth, his experiences acclimating to human culture provide Robert A. Heinlein with a platform from which to hold forth against everything he believes is wrong with politics, religion, and human relations. The book’s direct allusion to Gulliver’s Travels by Jonathon Swift might give readers some idea of the degree of satire to expect within its pages.
Among Mike’s many unusual talents acquired on Mars–including photographic memory, levitating objects, leaving his physical body, kissing well (according to Jill), and turning humans ninety degrees to everything else so that they disappear forever–is a linguistic quirk called “grokking.” One of Mike’s close friends, or water brothers, explains it well:
‘Grok’ means all of these. It means ‘fear,’ it means ‘love,’ it means ‘hate’–proper hate, for by the Martian ‘map’ you cannot hate anything unless you grok it, understand it so thoroughly that you merge with it and it merges with you–then can you hate. By hating yourself. But this implies that you love it too, and cherish it and would not have it otherwise. …’Grok’ means ‘identically equal.’
According to this intriguing concept, you can grok a person, grok a concept, grok an experience. Despite the bizarre degeneration of the plot in Part Three (of five) into a strange sort of fanatical religious sect / nudist colony, Mike eventually groks humanity. Unfortunately, it does not grok him back.