Dear Reader,

In this page, I intend to answer questions posed
to me by readers of CAUSALITY on issues
of general interest. I welcome such questions,
especially those touching on the controversial
status of causation, its meaning, its historical
development, how it is taught in classrooms
and how it is treated in textbooks and research
articles. Your questions and comments will be posted
anonymously unless I receive your permission to
include your name.

Judea Pearl

From: At the request of many readers
Subject: d-Separation Without Tears

Date: March 22, 2000
From David Bessler (Texas A&M University)
Subject: Bertrand Russell on Causality

Date: April 24, 2000
From: Nimrod Megiddo (IBM Almaden)
Subject: Simpson's paradox and decision trees

Date: April 24, 2000
From: David Kenny (University of Connecticut)
Subject: Causality and the mystical error terms (pages 162-3)

Date: May 11, 2000
From: Keith A. Markus, John Jay College of Criminal Justice, CUNY
Subject: Reversing Statistical Time (Chapter 2, p. 58-59)

Date: May 18, 2000
From: Jos Lehmann (University of Amsterdam)
Subject: Counterfactual notation in Chapter 7

Date: June 10, 2000
From: Dennis Lindley
Subject: On functional models for predicting the effect of actions

Date: June 28, 2000
From: Dennis Lindley
Subject: On causality and decision trees


Date: July 3, 2000
From: Dennis Lindley
Subject: On causality and decision trees (cont)


Date: July 25, 2000
From: Judea Pearl (UCLA)
Subject: General criterion for parameter identification (Chapter 5, pp. 149-154)

Date: September 2, 2000
From: Jacques A. Hagenaars, Tilburg University, The Netherlands
Subject: Indirect effects in nonlinear models

Date: September 15, 2000
From: Dennis Lindley
Subject: Reciprocal links in structural equations

Date: September 15, 2000
From: Mr. Asha (from Russia)
Subject: The impossibility of asymmetric causation

Date: September 22, 2000
From: Many readers
Subject: Errata list for the 3rd printing of Causality

Date: November 17, 2000
From: Jonathan Wilson, Surrey England
Subject: Defending the causal interpretation of SEM (or, SEM survival kit)

Date: November 25, 2000
From: L.B.S., University of Arizona, and S.M., Georgia Institute of Technology
Subject: Can do(x) represent practical experiments?

Date: December 1, 2000
From: L.H., University of Alberta and S.M., Georgia Tech
Subject: The causal interpretation of structural coefficients

Date: December 4, 2000
From: Many readers
Subject: Homework, or Gentle Introduction to Causal Models

Date: December 20-22, 2000
From: Bill Shipley, Universite de Sherbrooke, (Quebec) CANADA
Subject: Is the do(x) operator universal?

Date: December 26, 2000
From: Nozer D. Singpurwalla, The George Washington University
Subject: Has causality been defined?

Date: December 28, 2000
From: Many readers
Subject: Identification versus Correctness

Date: January 1, 2001
From: Les Hayduk, University of Alberta
Subject: On the Causal Interpretation of Path Coefficients

Date: April 27, 2001
From: Erich Battistin, University College, London
Subject: Intuition for tight bounds under noncompliance

Date: May 21, 2001
From: A leading statistician (prefers to remain anonymous)
Subject: Is the do-calculus sufficiently fundamental?

Date: July 30, 2001
From: Two Anonymous Statisticians
Subject: Why isn't confounding a statistical concept?

Date: September 28, 2001
From: Sampsa Hautaniemi, NIH

Date: October 24, 2001
From: Melanie Wall, University of Minnesota
Subject: Indirect Effects

Date: February 16, 2004
From: Susan Scott, Australia
Subject: Causality (2000)

Date: February 16, 2006
From: Dr. Patrik Hoyer, University of Helsinki, Finland
Subject: The Meaning of Counterfactuals

Date: March 10, 2006
From: Arvid Sjolander
Subject: d-separation of counterfactuals

Date: April 24, 2006
From: Eliezer S. Yudkowsky, Research Fellow, Singularity Institute for Artificial Intelligence, Santa Barbara, CA
Subject: The validity of G-estimation

Date: May 8, 2006
From: UCLA Students in CS262Z (Seminar in Causality, Spring 2006)
Subject: Identifying conditional plans

Date: May 11, 2006
From: UCLA Epidemiology Class - EPIDEM 200C Methods III: Analysis
Subject: Back-door criterion and epidemiology

Date: February 25, 2007
From: Judea Pearl
Subject: Counterfactuals in linear systems