31 A sufficiently strong and accurate causal model can allow us to use rung-one data to answer runge-two queries.Without the causal model, we could not go from rung-one to rung-two.
31 The laws of physics,for example,can be interpreted as counterfactual assertions,such as 'Had the weight on this spring doubled, its length would have doubled as well.
因果之梯的第一阶回答的是what 第二阶回答的是how 第三阶回答的是why