  In this essay I discuss potential outcome and graphical approaches to
causality, and their relevance for empirical work in economics. I review some
of the work on directed acyclic graphs, including the recent "The Book of Why,"
by Pearl and MacKenzie. I also discuss the potential outcome framework
developed by Rubin and coauthors, building on work by Neyman. I then discuss
the relative merits of these approaches for empirical work in economics,
focusing on the questions each answer well, and why much of the the work in
economics is closer in spirit to the potential outcome framework.
