That's indeed the biggest problem with null. It can mean many different things, often at once. It can be the third state of any tri-state logic, either absorbin

That's indeed the biggest problem with null. It can mean many different things, often at once. It can be the third state of any tri-state logic, either absorbing ("unknown", NaN) or absorbed (`Maybe` monad in Haskell) or something else. Or it can be an object that responds to any message but does do nothing (a "black-hole" object). Or it can be just a placeholder for the actual value to come with no particular operation in mind and will fail on any use. All these properties are implicit when null is being used.