Wherever we look today in academia, scholars are rushing to defend the Enlightenment ideas of political and individual liberty, human rights, faith in scientific reason, secularism, and the freedom of public debate. Why the worry? These ideas are, after all, enshrined in the U.S. Constitution. And yet, to hear the defenders of the Enlightenment, they are under assault. There is no shortage of enemies—from mullahs and Christian conservatives to science deniers and left-wing post-modernists.

Defending the Enlightenment has become an academic cottage industry with various camps hunkering down behind their own interpretations, and, in good academic form, attacking others. But recently, a few leading scholars have decided that it was necessary to present their defenses to a wider audience. Lynn Hunt’s Inventing Human Rights: A History (2007) was one of the first of such works; her argument made the case for Enlightenment values and the “soft power of humanity” in light of the use of torture by the U.S. government, but also, implicitly, because of the rise of new superpowers, like China, which openly reject human rights while embracing scientific progress. In The Enlightenment: And Why It Still Matters (2013), Anthony Pagden traced a history of Enlightenment philosophy, defending it from “theocracies” and the “fringe of the Christian right” that deny ideas of scientific progress, political liberty, and “global justice.”

These books—and the overall defense—have some validity. In spite of the fact that the U.S. Constitution and Bill of Rights were founded on Enlightenment ideas, it is not clear how many Americans understand the relationship of the Enlightenment to such documents. Many deists—believers in the Enlightenment idea of a post-Christian mechanistic nature god, such as Founding Fathers Thomas Jefferson, Thomas Paine, and Ethan Allen—would, with their scorn of organized religion, have a hard time getting elected in most parts of the United States today. The abolition of torture and capital punishment, seen by John Adams and Jefferson as central to Enlightened society, is now political anathema in most of the United States. Even the scientific explanation of natural phenomena is generally rejected or ignored, with only 40 percent of Americans standing by the scientific finding that global warming is man-made. When George W. Bush won the 2004 election, Gary Wills characterized the victory as “the day the Enlightenment went out.” The ideas of the Enlightenment are going through a crisis in the very country founded on them.

All this makes Vincenzo Ferrone’s newly translated book, The Enlightenment: History of an Idea, compelling: Ferrone claims that the importance of the Enlightenment has not been its triumph, but its centrality in public debate. An Italian historian of philosophy and a specialist on the influence of Isaac Newton, Ferrone believes the Enlightenment must be defended not simply as a secular, political idea, but, most importantly, as what Ferrone calls a tradition of “critical thought.” Immanuel Kant defined the Enlightenment as the “progress of mankind toward improvement” through the “freedom to make public use of one’s reason on every point,” and Ferrone claims it is this critical process that has driven public opinion and politics, giving us the language of human rights, tolerance, and individual liberty. The long philosophical engagement with the idea of Enlightenment, from Voltaire in the eighteenth century down to our own time, is, for Ferrone, one of the great intellectual legacies of the Enlightenment itself. He allows that we can question the primacy of science and secularism, but not critical debate. Many great figures of philosophy who have been seen as critics of the Enlightenment are in fact, Ferrone argues, defenders of the Enlightenment tradition.

The Enlightenment began not only with books and pamphlets, but with an earthquake. In 1755, an earthquake flattened Lisbon, set it aflame, and then caused a massive tsunami that swept the Tagus River into the city, killing more than 40,000 people. Theologians claimed the disaster was divine retribution for earthly pride and sin.