That means if we had a system continuing containing two gas molecules, gas molecule A and gas molecule B, that means these two guys have no volume and they exert no force on one another, so they can't communicate. So in many different ways, molecule A is invisible to molecule B and molecule B is invisible to molecule A. And that leads directly into the following results pressure created by one gas molecule is independent of the pressure created by another gas molecule. In other words, the pressure that this gas molecule exerts on the walls of my system of my container is independent of what this guy exerts on my wall of the container. So to find the total pressure, my system of two gas molecules, I simply have to add up this pressure and this pressure. And that's exactly what B states.