Kent Anhari in The New Atlantis:
According to the best-known telling of the tale, Hippasus, a Pythagorean of the fifth century b.c., was drowned in the sea by his fellow philosophers while on a fishing voyage. Hippasus had disclosed a secret that, if made public, risked destroying the credibility of his school’s commitment to a cosmos governed by perfect mathematical harmony: The relationship between a diagonal of a square and its side cannot be represented as a ratio — it is “irrational.” This legend sets the stage in Irrationality: A History of the Dark Side of Reason, Justin E. H. Smith’s urgent missive to a Brahmin class wracked with anxieties about a world that seems to have lost its grip on reason.
Smith, a philosopher of science at Paris Diderot University, is motivated by an urgent sense that a milestone reassessment of the Enlightenment’s legacy, and of the role of reason in public life, is underway in the United States and elsewhere. The emergence of prominent public voices with open counter-Enlightenment sympathies — such as Steve Bannon and Peter Thiel — and the resurgence of jingoistic populism are good reasons to take notice. So too is the fierce battle being fought between self-styled defenders of the open society, such as Steven Pinker and Jordan Peterson (however tenuous their grasp of the philosophies they claim to champion), and heirs to the left-wing critical tradition that views Enlightenment ideals as instruments for the powerful to oppress the marginal.