Which rather leads us to wonder for the rest of our lives whether our purpose is any better than something merely 'pulled out of our arses' I would have thought.
Which would be a sight more meaningful if you could in any way show that the Jesus myth wasn't repeatedly pulled out of arses for almost two thousand year or so. Any philosophy can be dismissed as 'pulled out of your arse' if you want, it's hardly an attempt to engage, is it?
Unless you wish to elaborate on Dawkin's clichéd deepity.
I'd say it was fairly self-explanatory, really, which bit was it that you failed to grasp? There is no intrinsic 'purpose' to reality, or our presence in it. Therefore, individually and collectively it's up to us to decide for ourselves what purpose will be. I'm not sure how, exactly, you'd need that principle elaborated upon.
O.