So long, ephemeral consciousness called “Derek Parfit.”
Here’s a talk he gave in October 2015:
Some key points:
– However much you’re giving to effective charities is probably too little.
– Everybody should be vegetarian.
– You should have no more than two kids.
Point of disagreement: Parfit says here that it seems fairly likely that there aren’t other intelligent beings elsewhere in the observable universe. I don’t know if there’s a consensus on this, but any astronomer I know of (Carl Sagan, Neil deGrasse Tyson, Phil Plait, maybe others) takes for granted that there are such beings.
Will we ever see or communicate with them? Well, besides just how big the universe is, one hypothesis forwarded to explain why we haven’t already is that civilizations tend to destroy themselves shortly after developing technology sufficient to become spacefaring.
We’re, of course, currently in no danger of doing this. We’d have to do something really crazy like elect a president who’s publicly advocated for a nuclear arms race. Which is very unlikely to happen unless a foreign government were to successfully influence a presidential election.