What are interventions?
In this section, we’ll summarize what we’ve learned about interventions so far and introduce mathematical tools to describe them. Finally, we’ll use our newly acquired knowledge to implement an intervention example in Python.
The idea of intervention is very simple. We change one thing in the world and observe whether and how this change affects another thing in the world. This is the essence of scientific experiments. To describe interventions mathematically, we use a special 
-operator. We usually express it in mathematical notation in the following way:
The preceding formula states that the probability of 
, given that we set 
to 0. The fact that we need to change ’s value is critical here, and it highlights the inherent difference between intervening and conditioning (conditioning is the operation that we used to obtain conditional probabilities in the previous section). Conditioning only modifies our view of the data...
