So we have many options to block communication between A and J: control for B, control for C, don’t control for D (because it’s a collider), control for E, and so forth. Any one of these is sufficient. This is why the usual statistical procedure of controlling for everything that we can measure is so misguided. In fact, this particular path is blocked if we don’t control for anything! The colliders at D and G block the path without any outside help. Controlling for D and G would open this path and enable J to listen to A.
