There isn't one. At least one that you have a say in. Your purpose is to be a part of nature as you always have and always will be. Your purpose right now is to conduct yourself as you are, since that's how nature made you to be. You will die, as nature has purposed. You will be re-used as nature has purposed. You will never again be in the natural state you are currently in, but you will always be a part of nature.
Reflect frequently upon the instability of things, and how very fast the scenes of nature are shifted. Matter is in perpetual flux. Change is always and everywhere at work; it strikes through causes and effects, and leaves nothing fixed and permanent.
The only constant is nature. If it has a purpose, you have found yours.
The question doesn't even make sense. You have to redefine it to "purpose" or some other word to even get started. The only literal interpretation is "what does 'life' mean?", which is just something like "a metabolic system capable of Darwinian evolution".
Life itself, the propagation and continuation of it, the creation of conscious structures capable of experience, reflection and influence over their nature - and ultimately defiance against a cold and dead, seemingly endless universe.
Or, for people that like the cold universe, there's a quote I forgot who it came from: "The purpose of life is to waste the energy of the sun"
I think we should qualify the question. I think I'd like to hear a reason for society as a whole to exist that is reasoned and has a firm basis in logic and has no emotive or circular reference.
Because I cannot see the point of it (and I've been accused of being a pessimist, depressed and worse for expressing this opinion). So, I would really like to hear an actual reason for us all to be here.
I don't think it needs one, and no idea if you mean existence of everything, or a single human life. But for my single human life my goal is to enjoy being physically embodied while I am, experience things using this body and its built-in equipment. All the things that will be impossible to do once dead, all the stuff you couldn't do before you were born. See things, move, dance, read, fuck, eat, hurt, feel everything. Think about things. Now while I am alive in a body that can do all that stuff.
Glad to meet you, Mr. Morningstar and I guess you'd be an authority on this. I agree, consciousness is the universe experiencing itself. And no, I don't need a favor, thanks!
I'd argue its the opposite, fight entropy until you drop dead. We are here because of a coincidence that didn't defy entropy but temporarily disrupted it, so disrupt that shit more, everything good came from balancing and lowering entropy.