The two reasons that you have listed are good reasons for why Chris McCandless wanted to go out into the wilderness. Keep in mind that McCandless's passion to be out in the wilderness did end up killing him; however, he also managed to survive living in the wild for quite some time before he even began his Alaskan debacle. McCandless passed away during the trip, so Krakauer couldn't ask him why he chose to live like that. Readers are left to come up with our own reasons, but McCandless's letter to Franz is really good support of the two reasons that your question has already listed.
The very basic core of a man’s living spirit is his passion for adventure. The joy of life comes from our encounters with new experiences, and hence there is no greater joy than to have an endlessly changing horizon, for each day to have a new and different sun.
Notice how McCandless emphasizes the passionate pursuit of adventure. He longs for the endlessly changing horizon. McCandless continues his letter...
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