This is at once a wise and wonderfully enjoyable book. Mark Lilla treats weighty matters with a light touch, in an elegant prose style that crackles with dry wit. Almost every one of the short sections into which the narrative is divided – and there is a narrative, cunningly sustained within what seems a relaxed discursiveness – takes careful aim and at the end hits the bullseye with a sure and satisfying aphoristic thwock.

The central premise of the book is simply stated: “How is it that we are creatures who want to know and not to know?” Lilla, professor of humanities at Columbia University, New York, and the author of a handful of masterly studies of the terrain where political and intellectual sensibilities collide, is an acute observer of the vagaries of human behaviour and thought in general, and of our tendency to self-delusion in particular.

He has a genius for the telling epigraph, of which there are many here, set like jewels throughout the text. The first of these, and the most emblematic, is taken from George Eliot’s novel Daniel Deronda: “It is a common sentence that knowledge is power; but who hath duly considered or set forth the power of ignorance?” This latter form of power, he tells us, is the subject he means to address.

His book is certainly timely. As he notes, there are certain epochs, and surely we are slap bang in the middle of one, when “evident truth” is cast aside in favour of all manner of imbecile imaginings. “Mesmerised crowds still follow preposterous prophets, irrational rumours trigger fanatical acts, and magical thinking crowds out common sense and expertise.” There, encapsulated in a sentence, is the predicament we face in our present-day social and political lives.

At the outset he presents a subtle retelling of Plato’s allegory of the cave. In his telling, a man and a boy are set free from the shadowed chamber and led up into the light. Soon, however, the boy is begging to return to the realm of happy delusion. “I miss my playmates,” he says tearfully. “Even if they were just pixels on a screen.”

From the cave, Lilla makes a smooth ascent to the case of Oedipus, the most famous exemplar of the will to ignorance. As he notes, today Oedipus the King “seems less about fate and prophecy than about the vexed problem of self-knowledge”. And Oedipus is not alone in his state of willed blindness. What about Jocasta? “While sharing her son’s bed all those years, wouldn’t she have noticed his disfigured feet, an unmistakable sign of his identity?” And why stop with the royal couple? Maybe they were all in on it, all of Thebes, and beyond, all “caught between the will to know and the will not to know”.

It is remarkable how many instances Lilla finds of the wriggly measures humankind adopts in order not to look the facts in the face, from the Bible – that vast compendium of elaborate avoidances – through Augustine, and the giants of the Enlightenment, to the enraptured messianism of the twin mid-20th-century ideologies of fascism and communism.

At the heart of the book is an invigorating excursus on St Paul, the founding father of the most consequential and, some would contend, most pernicious religious cult the world has known. Lilla knows his man: “It is no exaggeration to say that the history of western populism – spiritual and political – began with Paul.” He is “the cultured despiser of culture”, “a learned fanatic of the highest order”, who “held up as spiritual models innocent children, uneducated workmen, and lambs with vacant eyes, forever enshrining reverse snobbery as a Christian virtue”. If the next resident at 1600 Pennsylvania Avenue is in need of a patron saint, surely Paul is the one:

“For it is written, I will destroy the wisdom of the wise, and will bring to nothing the understanding of the prudent … If any man among you seems to be wise in this world, let him become a fool, that he may be wise.”

And one more quote, not to be resisted for the tenor of its measured contempt: “Paul made possible the transformation of the Gospels’ beautiful moral ideal into an anti-intellectual ideology that was enshrined permanently in the Christian scriptures and has since passed into our secular societies. That ideology has attracted a certain sort of mind ever since – one with a death wish.” As Nietzsche put it: “There was only one Christian, and he died on the cross.”

Ignorance and Bliss is a splendidly invigorating antidote to the vapid nostrums and mindless pieties – from right and left – that swirl about us in a poisoned fog. These are parlous times, and we need the likes of Lilla to help us face, and face down, the massed cohorts of “holy fools and eternal children whose distaste for the present sends them rushing, vainly, to restore an imagined past”.

• Ignorance and Bliss: On Wanting Not to Know by Mark Lilla is published on 12 December by C Hurst & Co (£18.99). To support the Guardian and the Observer order your copy at guardianbookshop.com. Delivery charges may apply