The Hardness of Reasoning about Probabilities and Causality

We study formal languages which are capable of fully expressing quantitative probabilistic reasoning and do-calculus reasoning for causal effects, from a computational complexity perspective. We focus on satisfiability problems whose instance formulas allow expressing many tasks in probabilistic and causal inference. The main contribution of this work is establishing the exact computational complexity of these satisfiability problems. We introduce a new natural complexity class, named succexistsR, which can be viewed as a succinct variant of the well-studied class existsR, and show that the problems we consider are complete for succexistsR. Our results imply even stronger algorithmic limitations than were proven by Fagin, Halpern, and Megiddo (1990) and Moss'e, Ibeling, and Icard (2022) for some variants of the standard languages used commonly in probabilistic and causal inference.