The idea of back-up, or redundancy, thinking comes from the engineering discipline -

Designing bridges with a safety factor that can comfortably handle the maximum volume of traffic, high winds etc.;
Building a power grid that can safely handle the peak load;
Using preventative maintenance - replacing/servicing components within their predicted lifespan - to ensure that aircraft do not fail in flight, using the Mean-time-between-failure (MTBF) benchmark;
Using data back-up systems.

Back-ups and redundancy are required because systems have break points and limits.

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Peter Bevelin describes the idea in 'Seeking Wisdom':


See interactive ebook on iBookstore