Naturalism and Norms

My recent exchange with Taner on ethical naturalism (EN) prompted a good bit of stimulating comment and criticism. I've been out of town for a couple of weeks and away from blogging, so I have not been able to reply to each comment as it arrived. Rather than attempt to do so now, I would like to address the issue that seems to me to be at the heart of much of the discussion: How do naturalists