Graphical methods for investigating causality, the related [confounder] tag, do-calculus, interventions, and counterfactuals.

Causal diagrams provide a highly intuitive graphical method for investigating both interventions and counterfactuals. Perhaps most importantly, causal diagrams provide, finally, an unambiguous definition of a confounding variable: a confounding variable is a variable that sets up a backdoor path from the investigated cause to the investigated effect.