I'm debating a strong evangelical at work, and I've got him pinned to his strongest reason for belief: that there would be no purpose to his life without god. Of course I know that isn't true, but I want to respond to this thoughtfully. How would you respond to the statement there is no purpose without God?
Some would answer that our purpose is to be with God, but that's a self-fulfilling prophecy. So we create this idea, call it God, to justify the intangible parts of life and give us "purpose", but our purpose is merely just to BE with that very thing that we created just for the sole reason of having a purpose? Am I the only one that finds this a little creepy? Okay. Flip side. God creates us for the sole purpose of having a fan club and some company. But we're separated by something called real life and apparently invisibility. Why the purposeful separation? And what is our purpose while we're here? Isn't it the exact same reasons that people of other beliefs and no religions give themselves? HELLO!
I'm not sure that we can respond to the general statement, "there is no purpose without God" unless we define what that purpose might be.
First I'd ask him to identify what he considers his life purpose to be. (Carrying on the species, being kind to others, spreading the word of God, contributing in some meaningful way to the benefit of the planet...?)
Then you can tackle whether God needs to exist for his purpose to exist. If the purpose is something like being kind to others, then clearly no God is required (and you can explain how kindness and co-operation are moral qualities that are not dependent upon a higher power.)
If his purpose is to spread the word of God, you can still break down the argument. That purpose doesn't require God's existence either; it merely requires his belief in a set of principles that he attributes to God.
People have been promoting a variety of gods throughout history ranging from Thor to Zeus. Presumably he'll agree that Thor doesn't exist, but that presumably there were Scandinavians, way back when, who found purpose in promoting Thor's ideas. Will he claim that their lives lacked purpose because Thor wasn't real? Would they not have felt driven by purpose through their own belief? (I expect that he'll argue over this, but at least if you can agree on a definition of his purpose, you'll have something to work with.)