How is Chris McCandless a visionary in the book Into the Wild?

Chris is a philosophical thinker who strives to put his
grand thoughts into action. Much like Henry David Thoreau (one of Chris's idols),
McCandless tries to make the idealized life of "simplicity, simplicity, simplicity" a
concrete reality. Much like a transcendentalist, Chris rejects the materialism that
consumes so many of the other people he witnesses and desires to live an honest life
closer to nature and close to God.  However, Chris’s idealism proves to be his downfall
as he ventures into the Alaskan wilderness completely unprepared for his adventure in
terms of equipment, knowledge, and experience. Alaska proves to be more challenging than
he anticipates and, ultimately, McCandless’s vision proves to be
unsustainable.