Via the Douglas Rushkoff blog.
It's an interesting question and one that I'm going to have to think about before answering. In the mean time, John Brockman, Publisher and Editor of the science web site Edge.org asked that question to over a hundred scientists and intellectuals. Some of the answers seem to be just an excuse to show off how much they know about their chosen subject, but most are wonderful to get your brain moving.
I think that the thing I believe, but cannot prove, is that there is a meaning for life. I don't necessarily believe that it is based on any divine purpose, nor do I expect to understand what it is.
Some years ago I remember hearing a basketball colleague state quite openly and brazenly that the sole purpose for humanity was to maintain and propogate the species. No reason, no outcome, just "go forth and multiply." I couldn't stand the idea. I felt it to be hollow and purposeless. If the whole purpose for life turned out to be the creation of more life, then I could see no reason not to just pull the pin, drop the bomb and do the Universe a favour.
Since then I've thought about the issue, in particular a paragraph towards the end of "A Brief History of Time" where Hawkins writes about the work towards a Grand Unified Theory of the universe and the increase and specialisation of scientific knowledge through the 20th Century. He commented that in the 19th Century, most scientists had a fair understanding of other fields of knowledge. However, when Einstein published his Theory of Relativity there was a lack of understanding by even the most brilliant minds of the time. In modern times, however, the concept is taught in Secondary Schools. In the same way, scientific knowledge today is highly specialised such that the only people that can understand most of the recent breakthroughs in any detail are, themselves, specialists in the same field. As time goes on, and should a Grand Unified Theory be realised, it will only be understood by a few brilliant minds. However, as time goes on it will take the artists and the philosophers in society to take that knowledge and explain to mankind what it means to us as humans.
I believe, but cannot prove, that mankind's reason for being here is to maintain until that time; to push towards an understanding that may not come in our lifetimes, or even our children's lifetimes, but rather to understand that the path to enlightenment is multi-generational, and that to maintain a world that values the work of scientists, artists, philosophers, you need to create people that value people.
It may wind up that the Buddhists have it right, and that when we find the answer it turns out to be creating such a world that values the here and now, and looking after the life around us.
Well, we can dream.
What do you believe is true, even though you cannot prove it?