Existential Difference between World States relates to differences between Objects existing. Given a World State from Agent ’s perspective where it has either 8 or 10 dollars, Existential Difference is defined as the minus () operator, and results in . A converse operator can be applied using addition ().
Note that changes between Objects can also be defined in terms of Existential Difference. The difference between a world with a brand new car and one where the same car is dilapidated can be expressed as subtraction of the new car, followed by immediate addition of the dilapidated one.