A quantum mechanical state corresponds to the value of a single dice. For example, "the dice under the green cup has a value of two." Einstein argues that quantum mechanics is not complete as it does not specify the value of the other dice. However, Bohr argues that there is actually only one dice that is sometimes under the green cup and sometimes under the blue one. So it makes no sense to talk about a dice that can not be seen. And it is never possible to look under both cups at the same time. For this reason, quantum mechanics describes everything that can be said about the dice.