I'm not sure which one of these apparently flatly contradictory proverbs I heard first but I have definitely heard both several times. One of them is:
There is honour among thieves.
No honour among thieves.
Do they simply mean the opposite of each other, therefore, at least in my mind cancelling each other out, or is there a subtlety here that I am not picking up on? Are they related, perhaps sharing an origin and then somehow becoming inverted?