mathematics, given the right situation, can eliminate the effect of confounders even without data on the confounder. And the situation can be clearly recognized. Anytime the causal effect of X on Y is confounded by one set of variables (C) and mediated by another (M) (see Figure 7.2), and, furthermore, the mediating variables are shielded from the effects of C, then you can estimate X’s effect from observational data. Once scientists are made aware of this fact, they should seek shielded mediators whenever they face incurable confounders.
