We now ask the counterfactual question “What if we had set the vaccination rate to zero?”

“Whenever you make an event happen,” we tell the computer, “remove all arrows that point to that event and continue the analysis by ordinary logic, as if the arrows had never been there.”

instead of representing probability in huge tables, as was previously done, let’s represent it with a network of loosely coupled variables. If we only allow each variable to interact with a few neighboring variables, then we might overcome the computational hurdles that had caused other probabilists to stumble.

My emphasis on language also comes from a deep conviction that language shapes our thoughts. You cannot answer a question that you cannot ask, and you cannot ask a question that you have no words for.

path coefficient represents the amount of variability in the target variable that is accounted for by the source variable.

A very direct way to predict the result of an intervention is to experiment with it under carefully controlled conditions.

imagining and comparing the consequences of several hunting strategies.

There are no arrows leading into X, therefore no back-door paths. We don’t need to control for anything.

after the inference engine has received the Data input, it will use the recipe to produce an actual Estimate for the answer, along with statistical estimates of the amount of uncertainty in that estimate.