How to define P(doom) and why it matters

The usefulness of p(doom) is controversial, but also it is tricky to even define since the usual ways we think about credence don't work with apocalyptic events. Not too tricky, but tricky enough I figured it would be worth writing up a note on it! In the process I also hope to show why it is useful, and why it is definitely not "an astrological sign" if used correctly. AI disclosure: No AI, just my meat brain this time! (Not counting spell check or search engines.) How we usually think about cr...