Holmes's D&D Excerpt

Do you wonder where the tradition of the asshole thief who steals from her own party started?

"Thieves are not truly good and are usually referred to as neutral or evil, so that other members of an expedition should never completely trust them and they are quite as likely to steal from their own party as from the Dungeon Master's monsters."

Baked right into the rules by, at least, Dr. Holmes's D&D, page 6.