DAG your pardon? Directed acyclic graphs in the causal wonderland

We’ll start this section by reviewing definitions of causality. Then, we’ll discuss the motivations behind DAGs and their limitations. Finally, we’ll formalize the concept of a DAG.

Definitions of causality

In the first chapter, we discussed a couple of historical definitions of causality. We started with Aristotle, then we briefly covered the ideas proposed by David Hume. We’ve seen that Hume’s definition (as we presented it) was focused on associations. This led us to look into how babies learn about the world using experimentation. We‘ve seen how experimentation allows us to go beyond the realm of observations by interacting with the environment. The possibility of interacting with the environment is at the heart of another definition of causality that comes from Judea Pearl.

Pearl proposed something very simple yet powerful. His definition is short, ignores ontological...