1. Confusion regarding the difference between catastrophes causing human extinction and catastrophies non-fatal to our species

There is a tendency to conflate global catastrophes causing the extinction of mankind (existential risks) and other enormous catastrophes which could bring about major civilizational damage without being completely fatal (most conceivable nuclear war scenarios, for instance). The defining features of existential disaster are irreversibility and totality. If there is a disaster which wipes out 99.9% of the world's population, 7 million humans would still remain in the planet's refuges, about 400-4,000 times the number of humans that were alive at the time of the Toba catastrophe 77,000 years ago. This would be more than enough to start over, and they would have a tremendous amount of intact records, technology, and infrastructure to assist them. So, the difference between a disaster that wipes out 100% of humanity and merely 99.9% of humanity is immense. Even the difference between a disaster that wipes out 99.999% of humanity and 100% would be immense. People seldom intuitively grasp this point, and it may have to be explained several times.