On Economic Debate--the ad hominem index

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.


Although I generally agree, it's worth taking into account the fact that Krugman writes for a major newspaper, while Mankiw writes a personal blog.

Krugman also has a Nobel Prize. Nothing to significant.

Just so you know, he dropped the link to this article on his blog. He seemed pretty flattered.

What has the medium in which Krugman writes to do with anything? Has the image of the "major newspaper" really disintegrated to the point that ad hominem attacks on their pages are so commonplace as to be excused?

Dude, have you seen Mankiws ad hominem attack on Keynes on june 26th? Do your homework!

Krugman writes for the readers of the New York Times and Mankiw writes the most popular college economics textbooks available today.

While this leads to a differences in their writing styles, there's more to it than that. To be specific, I think Mankiw has an easier time of writing respectable arguments because he's a nice guy and Krugman has a hard time doing the same because he's a jerk.

In his June 26 post, Mankiw was not debating, nor ever has debated, Keynes. In addition, Mankiw's most inflamatory paragraph is prefaced by the phrase explaining that he is paraphrasing the quote from Scott Sumner.

"ad hominem attacks are an indicator of the weakness of an argument"

What kind of middle school pseudo-psychology is this?


Wouter is correct. This savage takedown of Keynes as an investor is beyond the pale.

Next thing you know, Mankiw could like to an article critical of Congress!


I think you should do your own homework. That entry was an excerpt from another economist's (Scott Sumner's) blog.

Mankiw also writes for the readers of the NYT. See latest column on health reform last Sunday, which again provoked an irate response from Krugman's blog.

I increasingly think that Krugman has to be classed as intellectually dishonest.

... ooops! I guess that counts as an ad hominem attack against Krugman, so am not a saint like Mankiw.

Mankiw frequently writes the "Economic View" piece for the Sunday business section of the NY Times - the same major newspaper where one finds Krugman's op-eds.

Also, the entire Keynes post was directly quoted (as he made clear at the time) from Scott Sumner's blog.

Ad homs can be put to devastating use if your base argument is sound. Put up or shut up, as they say.

Can you say ad hominem? Seems like this guy missed the point of the blog

I think there is in this post a definite element of ad hominem attack against Paul krugman.

If anyone knows an Op-Ed columnist, then you'll understand there is above average (to say the least) number of deliberate attempts to generate Buzz -- maybe intentionally divisive, maybe not. But the incentive to stir the pot is obvious.

I don't think intelligent people actually use the adjectives that Krugman throws around -- and Krugman probably doesn't either, in his private life -- it borders on the realm of comic book villain and third-world dictator description.

Also, if anyone here writes (or attempts to) for a living, you know damn good and well the pickings are slim -- Krugman knows which side of his bread is buttered: how generate buzz and stay "relevant".

It's Krugman's choice (and mistake) every time he hits his self-parody button, by throwing long on a phony adjective fusillade. Besides, does anyone over the age of 35 takes the over-the-top act seriously? Krugman writes "hack" about some Ivy League mucky-muck -- intelligent people should read "kid on the schoolyard looking for attention."

Meanwhile Mankiw owns the copyright to his books IIRC. Not a lot of College authors can say that.

I think most of you all misunderstand exactly what an ad hominem logical fallacy is. It is not merely criticizing the opponent of your argument, it is criticizing the opponent of your argument WHEN IT IS IRRELEVANT TO THE ARGUMENT. This post is not an ad hominem attack on Krugman because the point of the post it to point out Krugman's use of ad hominem. Similarly, Mankiw's criticism is not an ad hominem attack on Keynes because the entire point of the post was that Keynes is not the savy investor everyone claims him to be, and he gives examples to back up his point.

IT's either one of two things about Krugman:
1) He is too tired of debating with arguments that he has decided to "go to the matresses". He is tired of being right and knowing he is right, that he decided to win the debate at any cost, because at the end people will see he was right all along.
2) Or, his nobel prize is a sign he is great at politics and at social relations because he knows how to win a debate without being right. His good (not nobel winning level) work as an economist combined with his skills in debating and politics has made him who he is. Someone who got the nobel not SOLELY for his work, but also for his skills in winning debates without being righ.
Which means, he knows how to make a fairly weak case, into a brilliant new undisputable insight.
HE's a showman.

Perhaps Paul has it in for Greg for one simple reason -- Mankiw's textbooks vastly outsell Krugman's.

Which may say something useful about what other economists think of Paul's reliability on matters beyond trade theory.

The main difference that I see between the writing of Mankiw and Krugman is that the second one intends to solve actual problems (a possible depression, quality of health care, etc.) while the first one is more concerned with consistency between his manual and public policies (when the latter do not coincide with his prescriptions there is something wrong in them).

In other words, Mankiw is a very detached economist which is more interested in Economics 101 than in making a better country for more people (which can be seen in his completely failed, in retrospect, public service). The opposite happens with Krugman, and, inevitably and appropriately, when you are doing politics (because that is what he is doing) you will consider the moral dimension (dishonesty, selfishness, unfairness).

Is Evans suggesting that we interpret Newton's ad hominem attacks against Leibniz with respect to the calculus as the rhetoric of someone who doesn't know what he's talking about? The claim in the post is flawed but does highlight an observation about stylistic differences of debating etiquette between Krugman and Mankiw. The proposition that an ad hominem attack implies ignorance or incoherence is suspect. Strictly speaking, an ad hominem attack, while distracting and rude, has no bearing on the truth or falsity of an argument, and Evans acknowledges this in the second paragraph. So why interpret the frequency of the ad hominem attack as an index of the strength of the argument and arguer? Rather, would it not make more sense to index the strength of the argument based on the strength of the argument? We should not let the ad hominem attack distract us from the main contours of the health care debate. That means not letting Krugman score points in the debate for his ad hominem attacks. But it also means not deducting points from Krugman for his ad hominem attacks.

VTL - ad homs ARE relevant to the entire structure of the argument in certain cases where there is a broad audience, and this is one of them. Since some of you fellers seem to have trouble understanding this, here's a greatly simplified example of why it may be necessary:

Mankiw: 1 + 1 = 3
Krugman: WHAT? Are you crazy? 1+1 of course is 2.
Math-challenged Audience: WHAT? But Mankiw is a Harvard professor. He can't be crazy.
Krugman: Right, he's not crazy, so here's a better more rational explanation -- he's being disingenuous for reasons having to do with maintaining a certain political reputation.

I don't blame Krugman. When confronted with a tide of opinion that is so spurious; what exactly would you like him to say? When government policy has for so long been tilted against the weak in society - you want him to be nice and polite about this? You call it ad hominem attacks. I call it righteous indignation.

Get real.

Cicero attacked Cataline; Martin Luther referred to the Pope as a "fart arising from Rome." Ad hominem attacks of this sort are merely rhetorical style or a way of raising the stakes in the debate.

There is no reason a rational debate can't include polemics.

Ad hominem is a logical fallacy. It is one of the ways someone defending an untenable position changes the subject.
It is a favorite of AGW supporters. They will never try to argue the science, they will call their opponent a "denier".
By the way, why didn't Krugman take Mankiw's bet in March?

"too" significant

While your average Joe may be familiar with the Name Krugman and not Mankiw, just ask anyone you can find with a recent econ degree whose work more influenced them and it's much more likely to be Mankiw.

Krugman's Nobel was at least partially motivated as a slight to President Bush and much of his work is more controversial than accepted.

When you read Krugman's columns or hear him speak, it often feels like he tries to force his theories to influence readers politically, while Mankiw comes across more objective and open-minded.

Simmmo, You're an idiot. I'd say how, but I'd just be a waste of my time, since everyone who agrees with me can clearly see how, and everyone who doesn't is to stupid to understand anyway.

I will make an ad hominem one: Krugs does politics, the low class kind, is intellectually dishonest & will do whatever he thinks necessary to "win" a debate.

let be honest here Greg Mankiw is an great economist open-minded and is a person who doesn't demonize or disparage a person he disagrees with. Krugman on the other hand is an accomplished economist but hes a partisan ideologue of the liberal-regressive I mean progressive persuasion who attack personally people who he disagrees with. Krugman seems to be blind of the failure of big government or the ineffectiveness / short comings of keynesian economics. Truth hurts paully

Krugman has been making ad hominem attacks for a long time, well before he started writing for the NYT.

In the old days his style was to say that someone who disagreed with him wasn't a "serious" or a "real" economist. He'd claim that his John Bates Clark award (best U.S. economist under 40, awarded every two years) was actually harder to get than the Nobel Memorial Prize in Economics because it was awarded less frequently. And so on.

It's his personality - not a tactic.

Your mommy will explain it when you are older.

Who makes more ad hominem attacks is difficult to say. In any case, if you are so against ad hominem attacks, why are you saying that Krugman relies on this? are you making ad hominem attack as well?

Besides, what seems more important is that Krugman has been right on most issues (e.g., Iraq war, the financial crisis), while Mankiw has been wrong. Did Mankiw say anything about the crisis in 2006 or even 2007? And why did Mankiw disallowed comments on his blog?

Mankiw writes the best-selling introductory textbook. OK. But given the dismal record of the discipline, is this necessarily something to be so proud about?

While it certainly is a fallacy to use ad hominem in debate, it is also a fallacy to think, the rest of the argument of a debater using ad hominem is weak. With Krugman i think it's more a result of intellectual arrogance and a lack of patience with others than a lack of well reasoned arguments if he uses ad hominem.

BTW, I really enjoyed the sh*tfight between Krugman, DeLong and Fama, culminating in this gem: http://krugman.blogs.nytimes.com/2009/01/29/the-sorrow-and-the-pity-wonkish/

"Eugene Fama, completely not getting it. Proposition 2 is wrong, because savings is an endogenous variable, not a fixed quantity.

This has become truly painful to watch."

His Nobel prize was awarded for contributions to international trade theory. Quoting the committee: "For his analysis of trade patterns and location of economic activity.

This has little to do with macro as understood in these debates.

Evans' argument is clearly intended to be disparaging of Krugman, but disguised as being objective and above the fray. VTL simply and correctly discusses the significance of an ad hominem attack, and seems to be the only one who's got it right.

I take this evaluation of the ad hominem index as an indicator of both the strength of argument and the strength of the arguer.

I have to say I sympathize with Krugman quite a bit. Sometimes you read a statement like this, and it's just ... stupid.

The use of ad hominem is not a sign of the weakness of one's argument; it is a sign of the weakness of one's personality. Krugman has been resorting to ad hominem attacks long before he wrote for The Times. Back during the Clinton years, he eagerly attacked fellow Democrats Lester Thurow and Robert Reich. Krugman is temperamentally unsuited to behave diplomatically.

That was a quoted from Scott Sumners blog. The part that Mankiw wrote was "An excerpt from Scott Sumners thought provoking blog"

Homework is done.

"Lowering the Plane of Regard"

Joseph Brodsky offers a lesson here, via Seamus Heaney:

"[Brodsky] was resolutely against any idea that put the social cart before the personal horse, anything that clad original response in a common uniform. ...

Not that he wished to use the sports stadiums for poetry readings. If anyone happened to bring up the huge audiences that attended such events in the Soviet Union, there would be an immediate comeback: "Think of the garbage they have to listen to." In other words, Brodsky decried the yoking together of politics and poetry ("The only thing they have in common are the letters p and o"), not because he had no belief in the transformative power of poetry per se but because the political requirement changed the criteria of excellence and was likely to lead to a debasement of the language and hence to a lowering of "the plane of regard" (a favorite phrase) from which human beings viewed themselves and established their values.

Let's be serious for a moment. Mankiw is a great economist who contributed to various fields, in particular to the mircofoundation of Keynesian economics. However, he has not established a new field. Krugman on the other hand has revived economic geography. At the same time, he is one of the most important scholars in international economics, both in trade theory and international finance. Only very few economists have important contributions in both sub-fields of international economics.
Mankiw might share a Nobel prize at some future point with other economists who worked on New Keynesian economics early on, but anyone who questions Krugman's Nobel prize cannot be serious. This is independent of whether you agree with Krugman's political views or not.

Krugman uses his ad hom attacks because he's a columnist who gets paid to attract readers and because as someone else said, he's an ideologue. Mankiw is an economist by trade, not a columnist (though he does appear in newspaper frequently) and his blog is free (for the time being). His incentives to attract readers through controversy is low.
That said, Mankiw is an empirical economist, Krugman a trade theorist. Both are economists but of different nature. A physicist and a biologist are both scientists, but when they disagree one would trust the opinion of the expert of the subject being debated. The same logic should apply here: When it comes to strictly international trade, Krugman probably has something intelligent to say, when it comes to actual macroeconomic outcomes, I'll follow Mankiw.

Also, the Bates Clark award is probably more prestigious than a Nobel prize because until this year it was a bi-annual award, and the Nobel committee has been known to be very biased. I'm more impressed with a Bates Clark than a Nobel, however both are incredibly notable.

Sorry for the short novel I've submitted.

I have this really clouded idea that, for reasons that I'm not entirely sure of, Liberal thinkers tend to be of opinion a.), below, while a few conservative thinkers, like Mankiw, tend to be of opinion b.). And then there is of course Fox News, Michael Moore, etc., who fall under neither of these categories.

a.) "The layman won't understand my complex argument, but because my complex argument is correct, I will therefore form a simple argument which he will understand, one that produces a result consistent with an understanding of the former, complex argument."

b.) "The layman won't understand complex technical aspects of my argument, but he will understand it conceptually in its principle. Because my argument is correct and understandable, I will therefore carefully articulate it as best I can."

For a.), Krugman, and most notably, on the extreme end of the scale, Marxists. Time and time again I see Marxists tout the complex, intellectually challenging nature of his theories. Theories that are just too difficult for them to make sense to anyone but other Marxists, apparently.

For b.), I think of guys like Kevin Murphy and Greg Mankiw.

And at my University, this thing seems to hold up pretty well among the professors.

Sorry, I overread that line.

But what kind of thoughts should that article have provoked? That Keynes was a fine economist?

The difference between Krugman and Mankiw is not that one uses rhetoric tricks, and the other one doesn't, but that Mankiw uses more clever ones.

Great post Rick. I haven't fully understood what ad hom. attacks were before this point. Very informative.

Sad that people insist on personal attacks. I respect both economists, and have noticed Krugman has a gruffer personality of the two.

Hopefully Saltwater vs. Freshwater doesn't split the economics world any more than it already is!

I agree that Mankiw is generally pretty polite.
Since my name was mentioned several times in comments I should point out that I try not to engage in ad hominem attacks. I've poked fun at Krugman a couple times, but always in what I thought was a light-hearted fashion. The Keynes quotation was a pathetic attempt at humor, that seems even more pathetic out of context (I also implied in the sketch that I was just envious of his good fortune.) In other places I have called Keynes a great economist.

"Krugman uses his ad hom attacks because he's a columnist who gets paid to attract readers..."

No. Krugman was into personal attacks *long before* he was a columnist, it's his character, the way his brain is wired.

Even his best bud for life Brad DeLong still says PK owes an apology to Laura Tyson for the attack he launched on her when he got passed over, and she didn't, for a job in the Clinton Administration.

Here's the apology the lawyers made Krugman publish in Slate after he libelled Fraga. Read that exchange -- PK turns gossip into libel and really believes he's bravely truth telling. But read Fraga's description of PK's operating methods, they haven't changed a bit since then.

Krugman is a perfect example of an ivory tower academic who doesn't know a thing about how the real world works -- and then when he sees something he doesn't understand, assumes it is evil he does understand and has to expose!

Example: He accused the partners of the Texas Rangers of heinous wrongdoing by paying fellow partner George Bush more than they took. Payoffs! Corruption! But the fact was the Rangers are a limited partnership, the other partners were passive no-risk investors, George was the actively-managing, personally liable general partner, which each LP has, who gets paid more for doing more work and assuming the LP's risk liabilities. There are about 14 million LPs in the US that operate that way, including just about all pro sports teams. It ain't a secret!

When the lawyers explained that to PK he wrote on his blog, "Gee, I didn't know that". (But he didn't apologize.) What a naif! Who deems himself qualified to tell how to restructure entire major industries.

My favorite example maybe is when PK was giving a talk (not writing a column) about the connections between economics and evolutionary theory, and swung into a totally gratuitous attack on Stephen Jay Gould, derided Gould's punctuated equilibrium as "evolution by jerks", and said Gould was as bad as John Kenneth Galbraith! A twofer!!

Like PK is qualified to judge paleontology ... or Gould had anything to do with the lecture subject ... or Galbraith had anything to do with evolutionary theory.

PK is a guy who just has never been able to control his name calling, and indeed considers it a virtue! Did you see his column yesterday? "Treason against the planet! Against the planet!" What the heck does that even mean, in English?

The examples like this are endless. It's how his brain is wired. And now that he has his Nobel, there's not a thing in the world to restrain him. It will never end.

Mankiw said that Krugman is not a marcoeconomist but an international trade theorist, which is clearly an ad hominem attack. Things are rarely black or white.

People who whine and complain about ad hominem are simply unwilling to deal with the mean of the argument, the core of issue at hand--instead they divert attention to the ad hominem "he hurt my feelings but I am oh so noble."

Anyone familiar with the debate amongst men (they were mainly men) of stature through history knows that ad hominem slips off the tongue of the best and brightest.

So what. Mankiw and others who complain about ad hominem should instead focus on the issue at hand.

They are cry babies.

(And while we're not on the topic--how many years will Mankiw continue to post those narcissistic references to quotes about his book. Yawn.)

Krugman is a trade theorist. To be an ad-hominem attack Mankiw would need to say he was a pathetic, and stupid trade theorist who could never understand macroeconomics.

Of course stating that would be almost completely untrue (while Krugman is a trade theorist he is most definitely not pathetic or stupid and I am sure he understands a good deal more than most about macroeconomics).

Personally I don't think anyone has avoided using an ad hominem argument throughout their entire career. Where you can distinguish between Mankiw and Krugman is that Mankiw seems to intentionally avoid personal attacks in his arguments while Krugman places personal attacks througout his.

Mankiw is attacking Keynes to be sure. He is simply using a quote from Scott Sumners because, in classic Greg Mankiw fashion, it allows him to avoid direct responsibility.

Trust me if I approvingly quote someone who insults you, then you will feel insulted.

Jose: Your characterizations of Mankiw and Krugman don't appear to agree with the actual record. If you look at Krugman's academic blog and his columns in the NYT, you'll find that he often says very inconsistent things in them. For instance, in 1999 Krugman was writing in his blog that we were in stock market bubble that was about to burst, and that he already saw the signs of a coming recession. Yet a few months later, in March of 2000, in his NYT articles he was assigning all the blame for the market dip on Bush.

Krugman has predicted 25 of the past 3 recessions. It was no more informative when he said we were headed for trouble than when Mankiw did not mention it.


1. Krugman (as Mankiw) can be wrong from time to time (I will gladly agree with that), and he can sometimes be even deceitful or dishonest. It is difficult, I think, to say something intelligent and truthful twice a week in a coherent column. However, his record is impressive. In topics that today are seen as the main world problems he has been talking since I remember and giving concrete and implementable solutions: 1. universal health care; 2. the wrongs of the motives and practice of Irak war; 3. the overpaid CEOs; 4. the increasing income inequality; 5. the house bubble; 6. the price manipulation in electricity markets; etc. The point is that he has been right most of the time.

2. But my general point was another: Krugman and Mankiw are very different economists, because the first one thinks that he has a political role to play (or of a normative economist), while the second considers he has to play just the role of a (positive) economist. In other words, Krugman tries to change values of people: something like "not caring for the poor, for the sustainability of the planet, for eliminating economic uncertainty, those are unacceptable values". That is why he includes the moral dimension: dishonesty, disingenuity, evil, etc. My position is that the creation of values is important, and to have an economist-preacher is a great thing with so many just political and religious preachers.

Mr. Mankiw writes for the New York Times every month with an editorial about economics. In any case, "taking into account" who employs whom can never justify an ad hominem attack.