"All colors are made of light, but black is the absence of light."

   "It looks like you covered all of the key issues, but you missed this one..."

   "I agree with everything you said but this one thing..."

   "I am not a lawyer, but it looks like it could be interpreted..."

I think you guys are just making these rules up, but maybe it is still good to keep them in mind, even if they aren't always true.