outcomes that make a true there is outcomes that make be true and then there's outcomes to make a and B through the intersection and the probability of a union B is probability of a plus probability of B minus probability of the intersection one abstract or abstract or concrete depending on your mindset way to think of it is that everything that can possibly happen is a point in this rectangle pictorially that's like every possible state the world could be in is a point in that rectangle I mean we might never know the