Land sakes you are unforgiving about those upvotes aren't you? I forget occasionally, I'm more concerned about responding.
"An organized set of beliefs involving a higher power and usually an afterlife, and which includes a set of rules or guidelines for how to live one's life"
Could that not also describe an athiest? The dichotomy being those who believe in a higher power and afterlife and those who don't. Your belief system still involves a diety and afterlife. Do you have a set of rules or guidelines that you use in your life or is it a free for all?