Conditions of sustainable civilizations

Theses on the conditions of sustainable civilizations

1. Sustainable civilizations manage to keep their population within limits, having neither growth nor decrease in the very long term
2. Sustainable civilizations do not consume anything nor do they produce unrecoverable waste. They use what remains available and what is replentished at the same rate. Carbon and hydrogen in various forms would seem prime candidates, while a lot of other materials we now use seem less plausible.
3. Sustainable civilizations manage to contain internal threats (e.g., conflicts) from reducing their population below critical lower limits or impeding its ability to pass on knowledge
4. Sustainable civilizations manage to avert destruction by external threats (e.g., asteroids, averse climates, reversal of magnetic poles). This would seem to require significant technical capabilities

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