Peng Ding

Cornfield shifted the burden of proof.

And the text details how this historical concept was recently generalized by VanderWeele and the author, Peng Ding, into a modern metric called the E-value.

The E-value is a formal quantification of Cornfield's logic.

It calculates the minimum strength of association that an unmeasured confounder would need to have with both the treatment and the outcome to fully explain away your observed causal effect.

It feels like a devastating blow to mediation analysis.

Does the book offer a way out, or does it just leave us hanging in an existential crisis?

Peng Ding does not leave us hanging.

The text presents alternatives that satisfy the Popperian requirement for physical observation, specifically the controlled direct effect in chapter twenty-eight.