Since I don't believe in a metaphysical plane of existent, in a human soul, or in anything divine, I am often asked by my theist friends how I explain consciousness. When I tell them that consciousness is just a biochemical process, well... they tend to laugh. What we are, who we are, and who we become, can all be traced to the processes that reside in our brain. When the brain is altered, we are altered, when the brain stops working, we are dead. My evidence for this is unscientific, but I think it makes sense. It comes down to what can happen to a person when their brain is damaged by injury, disease, or chemicals.
I know from experience that certain memories that I should have, are missing. I suffered a sever brain injury as a young man, and poof, about a four months of my life are gone. Plus, the three years previous to the injury are scrambled. I actually remember my freshmen year in High School well, but the next three are a jumble. I can't even remember the face of an old girlfriend. This injury is analogous to damaged sectors on a computer's hard drive. Something physically damaged the section of my brain which stored memories, just like something damaged the section of my hard drive that held my installation of Chess Master. If who we are can be taken away with a hammer... I don't see the hand of god, only biology.
The process becomes more complex with disease. People can change behavior. Who they are one day, can change to somebody entirely new the next. Take this parasitic infection for example:
A common parasite can increase a women's attractiveness to the opposite sex but also make men more stupid, an Australian researcher says.
If a parasite can change a woman's behavior, and the woman has no self awareness of the change, it follows that our concept of self and free will is essentially dependent on a biochemical process. The conclusion I draw from this is simple. We are the product of an incredibly complex biochemical process, and nothing more.
For more on this, read Modern neuroscience is eroding the idea of free will.
My theist friends find this thought appalling. They cannot grasp that we are not divinely chosen, but instead the product of evolutionary forces which have developed our brains to the point of self awareness. I find the thought comforting. It shows we are special, and fortunate. We should not take or intelligence for granted, it is not gift. We earned it.
I also hold that intelligence can be leaned, this too unscientific, but again I fall back on experience to help guide me. I attended university late in life. I did not even start the process until I was in my late 30s. In my undergrad and graduate programs, I leaned two new skills, writing and critical thinking. Both have dramatically improved my problem solving capabilities, and by extension, by intelligence (at least I think so, I still cannot spell).
One Man Hacking has a post on this concept:
If I remember correctly, it was in one of Edward de Bono's books that I first encountered the idea that thinking might actually be a skill, and thus learnable (and improvable by practice).
Over the years, this belief has been re inforced and I was forced to pull it all together yesterday when a friend asked me "How can I improve the quality of my thinking"?
What does this mean for Joe Atheist? We don't need the divine to explain who we are, what we are, or where we are going when we die. We need reason and science. We don't need Jesus to define a moral code. We are capable of reasoning it out for ourselves. We don't need James Dobson to tell us how to live and who to love. We intuitively know his message is evil. We don't need the mystical-all-knowing-one to explain the meaning of life. We are the meaning of life.