Not to trivialize all the posts in this thread, but almost everything everyone has written has been mentioned in some form in Mark Twain's "What is Man?"
Full text available here:
http://users.telerama.com/~joseph/mantble.html
That said, I don't agree with Twain's position, that everything everyone does is necessarily rooted in self-interest. While in my early college years, I was struggling to find a major and some way to serve the good of society yadda yadda yadda... the same confusing find-yourself stuff stuff that everyone does. Yet, at the end of the day, psychology and modern philosophies were telling me that, whatever it is I end up doing, it will ostensibly be because I thought it would help me, so I should just pick something and get it over with. Well, that didn't sit well, for a number of reasons, not the least because it was a completely erroneous notion. But how to demonstrate it?
Reductio ad absurdum!
I would take something about my life and destroy it - not for masochistic pleasure, but not even for the search of knowledge either (It must be already known that the thing itself will be destroyed and that there will be no gain). It was just because I could do it. It was not for me, but for "itself."
What a tragic experience. No, not a tragedy, but a farse! For didn't I already know with certainty the conclusion? There isn't a day that goes by that I don't regret it. I was almost immediately sad, deeply sad, and still am to this day. I have enough discipline so as to not fall into an cavern of mental illness, but, why... why did I do what I did? Was it to know? No, of course not. I already knew exactly what would happen, and everything happened exactly as predicted. I knew that I would be sad. Did I want to be sad? Well that's silly, obviously all people act in accordance to their self-interest and move towards that which will make them happy... right?
Nope. The philosophers and the psychologists are wrong. There was no benefit to me. I knew that I would be sad and now I am sad. There was no pleasure at all. There is no joking - it was most certainly
hell itself, being the conscious agent of the destruction wrought upon your own self. I don't feel wiser, advanced, or even experienced, for the experience was not necessary to know the experience. Certainly it is better that this hell is not experienced at all, by very definition. It is important to note that it was irreversible, for if it was reversible, there would have been a gain, if only in the form of a
regain. That such a pain is even possible is not only the falsification of necessary self-interest, but evidence of hell.
I hope this anecdote gives substance to the discussion. The only benefit is for you, the reader. (And, obviously, I would see no benefit or approval from you, for who would applaud a person who willfully and knowingly wrought sadness upon himself? Why, it wouldn't be in your self-interest!)
Oh, the things I do for you people.
(Note: I am not really laughing, but to soften the darkness of the issue for you

)