42 Tht main lesson for a student of causality is that a causal model entails more than merely drawing arrow.behind the arrows,there are probabilities.

42 translate the story into a diagram, listen to the query,perform a surgery that corresponds to the given query,and use the modified causal model to compute the answer

42 the knowledge conveyed in a causal diagram is typically much more robust than that encoded in probability distribution.

因果箭头的背后隐藏着概率关系。所以一般的查询因果步骤为先把故事形式化为因果图，进行干预，再用图将干预所得到的答案计算出来。