On Economic Debate–the ad hominem index

By Richard W. Evans on June 30, 2009 1:48 PM | 57 Comments
Anna Schwartz is the author of a book review that came out in this month’s (June 2009) Journal of Economic Literature on a recent biography of the economist and Nobel Laureate, Milton Friedman. One of her criticisms of the new Friedman biography is that the author missed one of the most important aspects of Friedman’s personality–his style as an economic debater. She says,

For example, Friedman’s style as a debater reveals an aspect of his personality. He was always courteous to his opponents in a debate, never attacked ad hominem. He concentrated on weaknesses of the opponent’s arguments and invariably emerged as the victor in the debate.

In addition to being a fallacious logical argument, ad hominem attacks are an indicator of the weakness of an argument. Ad hominem attacks reveal that the proponent either (1) does not understand the subject enough to make a sound argument, (2) is advocating a position that cannot be justified by logical reason, or (3) is simply using the debate as a platform to slander his opponent. Reasons (1) and (2) have relevance for judging the validity of the argument, but reason (3) is irrelevant.
Avoiding the logical fallacy of ad hominem in any type of argument is a skill to which all economists should aspire. My greatest respect is often reserved for individuals who exemplify this quality of Friedman in debate. Unfortunately, the ad hominem attack is commonplace in all types of policy arenas–economic, legal, political.

A more current example comes from the policy debate between two of the main thought leaders in economics–Greg Mankiw and Paul Krugman (Nobel Laureate). Regardless of your political ideology, let’s rank the arguments of these two economists in terms of an “ad hominem index.”

I regularly read the commentary from both Mankiw and Krugman in their blogs and in the newspapers. Notice that Krugman’s pieces include adjectives like “disingenuous”, “evil”, and “ignorant” in describing his opponents.

On the other hand, try to find an ad hominem point in any of the following Mankiw responses to Krugman statements (post 1, post 2, post 3). In fact, Mankiw goes out of his way to compliment Krugman on the points on which they agree (post 4, post 5, post 6). I couldn’t find any citations in which Krugman compliments or cedes anything to Mankiw.

I take this evaluation of the ad hominem index as an indicator of both the strength of argument and the strength of the arguer. Although ad hominem attacks often require less effort and seem to come most readily when angry, I aspire to be able to debate issues without resorting to destracting arguments attacking an opponent’s character. Thanks to Milton and Greg for teaching by example.

UPDATE: One aspect of this topic that I neglected to mention is that ad hominem arguments can be very effective, even though they should not be considered in the logical support of an argument in most cases. There is a large political science literature on the efficacy of negative attack ads in political campaigns.