This is where Lilienfield and his paper come in. What he calls the “microaggression research program” has been a daisy-chain of confirmation bias rather than a rigorous pursuit of scientific truth. Indeed, he says, the very concept of microaggressions is too hazy and ill-defined to be studied systematically, even by social scientists.

His “Microaggressions: Strong Claims, Inadequate Evidence,” published in the journal Perspectives on Psychological Science, is a tour de force. Lilienfeld undertakes a critical review of the literature that social scientists have produced on microaggressions. He begins, as he should, by conceding the fact of ongoing racism in the United States. He knows too that words can be unintentionally wounding. He points to an incident in which an engineering professor expressed surprise before his classroom when an African-American student got a perfect score on a test, apparently on the assumption that no black student could be expected to do such a thing. All of us have been witness to similar incidents of callousness and gaucherie. I once heard of a well-loved public servant who referred to a rival politician as “the first mainstream African American who is articulate and bright and clean.” Racial prejudice can indeed be insidious.

But is it ubiquitous? Does it soil even the most innocent encounter between persons of different races—or rather, between a white person and a person of another race? (In the scheme of microaggressions, a white person is ipso facto the perp.) The answer is, and Lilienfeld’s point is, we don’t know. Anecdotally it’s clear that words taken as a microaggression by one Latino or African American may go unnoticed by another. Despite such common experiences, which would seem to undermine many definitions of the word, no scientist has “challenged the central assumptions that microaggressions, as currently conceptualized, .  .  . comprise a psychologically meaningful construct.” The most important and worrisome claim of micro­aggression researchers is that microaggressions cause consistent and measurable harm to the mental health of their recipients—and yet no one has done a systematic review of the empirical evidence that supposedly establishes such a causal link.