What does Alexander supertramps manifesto on page 163 mean?

Two years he walks the earth, no phone, no pool, no pets, no cigarettes. Ultimate freedom. An extremist. An aesthetic voyager whose home is the road. Escaped from Atlanta. Thou shalt not return, ‘cause “the West is the best.” And now after two rambling years comes the final and greatest adventure, the climactic battle to kill the false being within and victoriously conclude the spiritual revolution. Ten days and nights of freight trains and hitchhiking bring him to the great white North. No longer to be poisoned by civilization he flees, and walks alone upon the land to become lost in the wild. – Alexander Supertramp, May 1992.”

This passage shows how McCandless feels about his journey so far, right after he walks into the wilderness. He is clearly proud of himself, and proud of what he has accomplished, and deeply excited for the Alaskan “greatest adventure.” It also shows, however, that he probably intends to rejoin civilization, even though he describes it as poisonous, for he calls this his “final” adventure, which will “conclude the spiritual revolution.”

And though he writes "Thou shalt not return", the implication is not that he is walking into the wilderness to die, but that he will not go back to the East (since over his two-year journey he has fallen deeply in love with the American West). Finally, the passage shows how intertwined his need for independence and freedom is with his inability to let people too close, as he likens his entrance into the wilderness to fleeing and emphasizes that he is alone, and that only now can he enjoy “Ultimate freedom.”