i, personally, see nothing contradictory about observing rituals from whatever tradition - ethic, national, religious - and being an atheist. i don't believe in god. that doesn't mean i'm blind to the value of ritual, or to the sacredness of life. whether we were called into existence by chance or by the word of god (i'm a biophysicist so i favor the first explanation), we are still remarkable, and worthy of wonder and reverence.