“The Misinformation Age,” Cailin O’Connor and Owen Weatherall, Yale University Press, 266 pages, $26.

“Alternative facts.” The term has become part of the vernacular, introduced anew by Kellyanne Conway, a Trump administration official. But while her phrasing may have been new, Conway was taking part in what has apparently become a conservative tradition — performing an extreme skepticism that dates back to Greek times.

Recall a high-ranking aide in the Bush administration needling a journalist for belonging to “the reality-based community.” Cailin O’Connor and Owen Weatherall, in their book “The Misinformation Age,” introduce their subject with the Vegetable Lamb of Tartary — a tree that reportedly grew gourd-like fruit filled with tiny lambs.

The claim was propagated during medieval times by so many respected naturalists and scholars that it took nearly four centuries before it was satisfactorily debunked. Those medieval scholars kept citing one another rather than verifying (or disproving) the Vegetable Lamb for themselves.

Social factors then and now are key to understanding the spread of belief, the authors wrote. For example, the authors show how industrial interests have repeatedly exploited any whiff of uncertainty to argue against government regulation.

The one thing you begin to notice in this book is that propagating a reflexive skepticism and sowing discord aren’t terribly difficult, especially when there’s a vested interest willing to pay for it; “merely creating the appearance of controversy” is often all that needs to be done.