 Determining the probabilities of counterfactuals, even just upper and lower bounds, is computationally demanding. Balke and Pearl’s twin network method (Balke and Pearl (1994a), (1994b); Pearl (2009, pp. 213 - 215)) and Richardson and Robins’ split-node method (Richardson and Robins (2016)) are two methods that have been proposed for solving this kind of problem.