[Phaedrus]

...nonexistence [of God] need not mean that humans have no purpose.

Care to expand on that? I think it's flat wrong. But let me take a step back. Do you think purpose is inextricably linked with consciousness? If not, why not? Do you think consciousness is real? It's certainly not material. Is anything real that is not material? And purpose certainly cannot be defined in mechanical terms -- that's a closed loop. Bottom line is you said a mouthful, with certitude, in a very few words but I don't think it will fly (to mangle my metaphors).

[Doctor Stochastic]

I don't get you point about conciousness. Conciousness may not be a material thing itself, but if the material is destroyed, the conciousness goes too. Like the Cheshire Cat's grin.

In terms of purose, each person seems to have his own purpose; purpose need not (logically) be imposed from the outside.