Kevin Drum sets off an intellectual WMD on his blog, writing about IQ and race. Sit back and watch the fallout spread across the blogosphere, with lots of posts of varying degrees of anger, tortuousness and smugness, depending. I could write a lot about this topic, but I’ll limit myself to two points. Kevin is begging the question, and he is equivocating between two senses of the word ‘intelligence’ in a way that makes his argument seem much more controversial than it really is.

First, the question begging. For Kevin, intelligence is like smut:

[I]ntelligence is a useful, everyday umbrella term that has genuine meaning. It is, roughly, the ability to deal with analytic complexity, and let’s face it: we all know it when we see it… In fact, the main reason that intelligence is such a hot button is that it so obviously is important. In a complex society, high intelligence is an extremely valuable commodity, and this makes the politics of intelligence both contentious and ideological.

He goes on to say:

Although the origins and effects of racism are long and complex, there’s little question that lower average intelligence is one of the big reasons that blacks do poorly in American society. The fact is that the black-white gap does exist, and it’s not merely a cultural artifact or the result of bias on standardized tests. It’s a very real thing and it needs to be attacked head on.

Kevin hasn’t really made his case. Instead, he’s assumed that it’s true and argued from there. He goes in one breath from “lower than average intelligence is one of the reasons that blacks do poorly in American society” to “The fact is that the black-white test score gap does exist, and it’s not merely a cultural artifact or the result of bias on standardized tests.” Kevin’s right that the black-white gap on test scores is something we can robustly measure. What that tells us about the usefulness of “intelligence” as an explanation for the gap is exactly what’s at issue in this debate. To simply assert that “there’s little question that lower than average intelligence” is what explains the gap is to assume precisely what needs to be proven. Rather than giving us a workable definition of intelligence, he just says “we all know it when we see it”.

Second, the equivocation. In the course of his post, Kevin discusses The Bell Curve. He thinks Herrnstein and Murray show convincingly that intelligence is a real trait and that it’s socially important. Then

there’s Part 3, in which the authors argue that the 15-point IQ difference between blacks and whites is primarily caused by genetic differences. And suddenly the quality of their arguments falls off a cliff… they vastly underestimate the power of environmental factors. Sure, intelligence is 50% hereditary, but that means it’s also 50% environmental. And that 50% is more than enough to account for a 15-point difference but only if you take seriously the wretched conditions that blacks at all socioeconomic levels face in this country.

In other words, the gap between blacks and whites on the only thing we can measure that might be related to underlying intelligence washes out when we take environmental factors into account! So where, exactly, is the controversy? I reject Kevin’s straw man: no-one is arguing that there’s no such thing as smart people in the “know it when I see it” sense he talks about. Things only get controversial (and racist) if you think there’s a persistent, measurable between-group difference on this trait between blacks and whites that can’t be eradicated by equalizing environments. But Kevin plainly does not think this is so, because he has just told us that the only measurable group-level test-score differences are explained by environmental factors! Which leaves us with the harmless proposition that the genetic component of intelligence is variably distributed across the population, but not in the basically racist way that Herrnstein and Murray insinuate.

Which leaves us with the question of why Kevin would post something that just cries out to be misinterpreted. The last four paragraphs of his post are taken up with ‘Do Not Shy From Harsh Truths, My Liberal Friends’ and ‘Face the Truth Head On’ stuff. That’s a seductive rhetoric for embattled liberals. You’re on the side of truth. You are being realistic. The conservatives like you. I’m all in favor of facing unpleasant truths, being a social scientist and all. But what’s so unpleasant about what seems to be the truth here?