Part 4 走向未来
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   *We have layered an artificial world atop the natural one.*
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   *Which do you think will stand the test of time?*
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   *The sooner we dovetail back to the natural,*
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   *the greater our chances for success become.*

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.. toctree::
   :maxdepth: 2
   :caption: Part 4 目录

   ch18
   ch19
   ch20
   Epilogue