Causal Analysis in Theory and Practice

Dear Nancy,

This letter concerns the issue of “causal plurality” which came up in my review of your book “Hunting Causes and Using Them” (Cambridge 2007) and in your recent reply to my review, both in recent issue of Economics and Philosophy (26:69-77, 2010).

My review:
http://journals.cambridge.org/action/displayFulltext?type=1&fid=7402268&jid=&volumeId=&issueId=&aid=7402260

Cartwright Reply:
http://journals.cambridge.org/action/displayFulltext?type=1&fid=7402292&jid=&volumeId=&issueId=&aid=7402284

I have difficulties understanding causal pluralism because I am a devout mono-theist by nature, especially when it comes to causation and, although I recognize that causes come in various shades, including total, direct, and indirect causes, necessary and sufficient causes, actual and generic causes, I have seen them all defined, analyzed and understood within a single formal framework of Structural Causal Models (SCM) as described in Causality (Chapter 7).

So, here I am, a mono-theist claiming that every query related to cause-effect relations can be formulated and answered in the SCM framework, and here you are, a pluralist, claiming exactly the opposite. Quoting:

“There are a variety of different kinds of causal systems; methods for discovering causes differ across different kinds of systems as do the inferences that can be made from causal knowledge once discovered. As to causal models, these must have different forms depending on what they are to be used for and on what kinds of systems are under study.

If causal pluralism is right, Pearl’s demand to tell economists how they ought to think about causation is misplaced; and his own are not the methods to use. They work for special kinds of problems and for special kinds of systems – those whose causal laws can be represented as Pearl represents them. HC&UT argues these are not the only kinds there are, nor uncontroversially the most typical.“

I am very interested in finding out if, by committing to SCM I have not overlooked important problem areas that are not captured in SCM. But for this we need an example; i.e., an example of ONE problem that cannot be formulated and answered in SCM.

The trouble I have with the examples sited in your reply is that they are based on other examples and concepts that are scattered on many pages in your book and, thus, makes it hard to follow. Can we perhaps see one such example, hopefully with no more than 10 variables, described in the following format:

Example: An agent is facing a decision or a question.

Given: The agent assumes the following about the world: 1. 2. 3. ….
The agent has data about …., taken under the following conditions.
Needed: The agent wishes to find out whether…..

Why use this dry format, you may ask, when your book is full with dozens of imaginative examples, from physics to econometrics? Because if you succeed in showing ONE example in this concise format you will convert one heathen to pluralism, and this heathen will be grateful to you for the rest of his spiritual life.

And if he is converted, he will try and help you convert others (I promise) and, then, who knows? life on this God given earth would become so much more enlightened.

And, as Aristotle used to say (or should have) May clarity shine on causality land.

Sincerely,

Judea Pearl

Clark Glymour writes:

Nancy Cartwright devotes half of her new book, Hunting Causes and Using Them, to criticizing "Bayes Net Methods"–as she calls them–and what she takes to be their assumptions. All of her critical claims are false or at best fractionally true. This paper reviews the literature she addresses but appears not to have met. Please click here to read further.

For related discussion, please see a previous post by Judea Pearl.

Judea Pearl writes:

A new book on causality came out last month, Hunting Causes and Using Them by Nancy Cartwright (Cambridge University Press, 2007.) Cartwright is a renown philosopher of science who has given much thought to the methodology of econometrics, and I was keenly curious to read her take on the current state of causality in economics.

Cartwright summarizes what economists such as Heckman, Hoover, Leroy and Hendry said and wrote about causal analysis in economics, she occasionally criticizes their ideas, and further discusses related works by philosophers such as Hausman and Woodward, but what I found surprising is that she rarely tells us how WE OUGHT to think about causes and effects in economic models. Given that economists admit to the chaotic state of affairs in their court, the role of philosophy should be, in my opinion, to instill clarity and provide coherent unification of the field. This I could not find in the book.

Additionally, and this naturally is my main concern, Cartwright rejects the surgery method as the basis of counterfactual and causal analysis and, in so doing, unveils and reinforces some of the most serious misconceptions that have hindered causal analysis in the past half century (see my earlier posting on Heckman's articles.)

I will focus on the latter point, for this will illuminate others.

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