> You are unlikely to leave a lasting legacy, and the generation you do affect, will die as well.

By this logic, culture and society would die every generation, and have to be rebuilt from scratch each time.

We all leave behind a "small" but far-reaching legacy that ripples out from our short lifetime. Each of the thousands of interactions we have with with other people and our general environment have a tiny but real impact that doesn't necessarily diminish to zero after we die. The change that occurs then has a small domino effect on any other person or system that it touches. And so on and so forth :)

My life today is deeply affected by the concerted actions of billions of unknown individuals from centuries and millennia past in ways that I can't even begin to fathom. I'm grateful for some of those impacts. For other impacts less so, but I hope to contribute small changes for the benefit those who live in the untold distant future.

I completely agree that wanting to make a positive impact on the world is important, although, and I don't want to sound too nihilistic here, the actual magnitude of that will probably be small for most people, therefore I think that personal satisfaction in life should be important and isn't meaningless, which was what OP claimed and the reason why I asked that question.

Yeah small and quickly diminishing over time, outside of very close friends and direct descendants. For example how many fought in WW2? How many were in high level roles and instrumental to the conflict? How many would be thinking they were making a lasting impact on the world? And of those what small portion have pretty much a permanent place in the history books?

Even to pick a small part of it, 130,000 people worked on the Manhattan Project but a history of it that the average person would consume might name 10 key figures.

The long-term impact of any human activity is so much more than what is written in a history book somewhere. A history book is an enormously compressed, somewhat distorted depiction of human experience. Only a very small sliver of the actual fiber of human culture, achievement, and experience across time is recorded in this way. Yet all of these things are still happening, and they form the substrate upon which the events that are actually written down can take place.

To use your example of the Manhattan project: only 10 people may be remembered in books, but they certainly would have never completed the project by themselves. The contributions of those other thousands of individuals was vital to the project's success. If they didn't exist, it's not a guarantee that you could have replaced all of them -- the project may have simply failed.

> We all leave behind a "small" but far-reaching legacy that ripples out from our short lifetime. Each of the thousands of interactions we have with with other people and our general environment have a tiny but real impact that doesn't necessarily diminish to zero after we die.

What you do in life, echoes in eternity.

Well, my point was really more that the orignal claim was explicitly talking about "at the end" of the timeframe, so we're talking about near death -- where putting weight on immediate gratification is harder to justify.

But to address your question: people 'take the limit' and argue that life is just meaningless in every way all the time. If it were true, you shouldn't be bothered to make that effort in the first place. Obviously your actions matter to other people by the sheer virtue of the fact that you're optimizing for it. if you weren't, you wouldn't have bothered to ask the question.

Sometimes life is what you actually do, not merely what you think.