Atheism and Purpose

[Darwinian]

Then I realized a startling fact: if there is no God who created me, then I have no purpose. No inherent purpose, no mission in life. If everything is chaos and natural selection, then I'm just a determined entity. I don’t have to worry about “purpose.” There is no purpose. I am free from my existential dilemma. Free at last.

Presumably then you do feel that you have a purpose. A purpose pre-destined by this God character. If so then I have to ask what that purpose is and to what end?

Also, chaos and natural selection barely have a nodding acquaintance so I'm not sure what that has to do with anything. Evolution works on the random mutation of genes that give its host some sort of advantage in the 'struggle for life'. This is not chaos. Perhaps you are alluding to the principle of cause and effect and that all future actions or events are already pre-determined by their past and so we can have no free will and any such sense is purely illusionary.

And why do you feel that you need a purpose or that a purpose is anything more than a human construct?

This I think is the fundamental difference between you and I. You look at the Cosmos and say "why", whereas I look at the Cosmos and say "how"! Correct me if I'm wrong.

Again, this isn't the reason why atheists are atheists as if you actually believe in a god then simply because you want to be free of purpose or to construct your own doesn't change the fact that you believe.