The introduction describes the inadequacy of early 20th century statistical methods at making statements about causal relationships between variables.

Reasoning on this level answers questions of the form 'if I make the intervention X, how will this affect the probability of the outcome Y?'.

Causal analysis using path diagrams is then introduced through the explanations of the work of Sewall Wright.

This chapter takes a historical approach to the question 'does smoking cause lung cancer?

', focusing on the arguments made by Abraham Lilienfeld, Jacob Yerushalmy, Ronald Fisher and Jerome Cornfield.

The authors then explain how causal reasoning (as developed in the rest of the book) can be used to argue that cigarettes do indeed cause cancer.

The chapter finishes with two examples, used to introduce the use of instrumental variables to estimate causal relationships.

The authors discuss the work of Barbara Stoddard Burks on the causes of intelligence of children, the 'algebra for all' policy by Chicago public schools, and the use of tourniquets to treat combat wounds.

Scientific background, excerpts, errata, and a list of 37 reviews of The Book of Why is provided on Judea Pearl's web page.

Maudlin also criticizes the section on free will for its "imprecision and lack of familiarity with the philosophical literature".

The review concludes by stating that "[t]his book is a must for any serious student of philosophy of science, and should be required reading for any first-year undergraduate statistics class".

[4] Lisa R. Goldberg wrote a detailed, technical review in Notices of the American Mathematical Society.