The principle of non-contradiction corresponds to traditional notions of reality: nothing can be something and can be not something at the same time (to be snow and to be not snow to be a quantum and to be not a quantum) or a single object can not simultaneously have the opposite qualities (to be high and low, positive and negative, salty and unsalted). In full compliance with the ontological obviousness of such an idea one of the main laws of logic is a law of non-contradiction.