 If we have a complete structural equation model, we can assign probabilities to counterfactuals, in light of observations. Let \(\bV = \{X_1, X_2 ,\ldots ,X_n\}\) be a set of endogenous variables, and \(\bU = \{U_1, U_2 ,\ldots ,U_n\}\) a set of exogenous variables. Our structural equations have the form: