Sentence:  Dawkins has received appreciative letters from people who were formerly what he derisively calls "faith-heads" who have abandoned their delusions and come over to the side of the <WSD>brights</WSD>, the pleasant green pastures where clear-eyed, brave, bold, and supremely brainy atheists graze contentedly. 
Meaning of the word marked with <WSD> tags:  A person with a naturalistic worldview with no supernatural or mystical elements.