The incoherence is that I also value purpose.
I know, but assuming you're a human and no aliens have messed with your brain, it's highly unlikely that this value is a terminal one.
Can you expand on this please? How do you know it's highly unlikely?
First, it doesn't seem like the kind of thing evolution would select for. Our brains may be susceptible to making the kind of mistake that leads one to believe in the existence of (and the need for) objective morality, but that would be a bias, not a terminal value.
Second, we can simply look at the people who've been through a transition similar to byrnema's, myself included. Most of us have successfully expunged (or at least minimized) the need for an Objective Morality from our moral architecture, and the few I know who've failed are badly, badly confuse...
Sometime ago Jonii wrote:
When I'm hungry I eat, but then I don't go on eating some more just to maximize a function. Eating isn't something I want a lot of. Likewise I don't want a ton of survival, just a bounded amount every day. Let's define a goal as big if you don't get full: every increment of effort/achievement is valuable, like paperclips to Clippy. Now do we have any big goals? Which ones?
Save the world. A great goal if you see a possible angle of attack, which I don't. The SIAI folks are more optimistic, but if they see a chink in the wall, they're yet to reveal it.
Help those who suffer. Morally upright but tricky to execute: James Shikwati, Dambisa Moyo and Kevin Myers show that even something as clear-cut as aid to Africa can be viewed as immoral. Still a good goal for anyone, though.
Procreate. This sounds fun! Fortunately, the same source that gave us this goal also gave us the means to achieve it, and intelligence is not among them. :-) And honestly, what sense in making 20 kids just to play the good-soldier routine for your genes? There's no unique "you gene" anyway, in several generations your descendants will be like everyone else's. Yeah, kids are fun, I'd like two or three.
Follow your muse. Music, comedy, videogame design, whatever. No limit to achievement! A lot of this is about signaling: would you still bother if all your successes were attributed to someone else's genetic talent? But even apart from the signaling angle, there's still the worrying feeling that entertainment is ultimately useless, like humanity-scale wireheading, not an actual goal for us to reach.
Accumulate power, money or experiences. What for? I never understood that.
Advance science. As Erik Naggum put it:
Don't know, but I'm pretty content with my life lately. Should I have a big goal at all? How about you?